dune - Did the big smuggling outfits operate interstellar vessels that were not controlled by the Spacing Guild?

A recent discussion reminded me of a friendly online argument I once had with another fan of Frank Herbert's Dune. This was at least twenty years ago, and it occurs to me that the disagreement was never resolved to our mutual satisfaction.

At the time, I said something to the effect that I took it for granted that the smugglers (as they operated during the first book of the series, at least, before Paul Muad'Dib became Emperor) operated entirely independently of the Spacing Guild, using smaller ships which were somehow capable of making successful interstellar voyages on their own. Since Guild Heighliners are so jaw-droppingly huge, it seemed likely that any cargo carried by the smugglers was statistically insignificant from the Guild's point of view.

In other words, I felt that according to the strict letter of Imperial Law, the Spacing Guild was supposed to have a 100 percent monopoly on interstellar transport . . . but in reality, they probably only had about a 99.9999999 percent monopoly in terms of "tonnage moved per year." That was probably close enough to let them tolerate the existence of small-scale smuggling operations without throwing a hissy fit about it. ("So all the smugglers in the galaxy, put together, only handle about one ton in every billion that travels from world to world . . . who cares?") I also suspected that interstellar smuggling was riskier and/or slower than shipping things via Heighliner, since it was pretty clear that the smugglers didn't have spice-addicted Navigators and Steersmen to use prescience to find the optimal paths for any long voyage.

My online acquaintance offered a different interpretation of the text of Dune -- one which I had not run across before. I believe his take on it was that the smugglers probably have short-range aerospace vessels capable of getting up off the surface of the planet, and way out beyond the breathable atmosphere, so that the cargo in the hold doesn't have to pass a customs inspection in a spaceport before take-off . . . and then the smuggler captain simply pays for his ship to hitch a ride inside a Guild Heighliner, parking it somewhere within before it heads out-system on its way to some other inhabited world. Once the smuggling vessel is aboard the Heighliner, no other passengers -- not even Imperial officials -- are allowed to poke their noses inside and take inventory of the cargo.

In my acquaintance's view of the matter: At the other end of the trip, the smuggler vessel flies out of the Heighliner and must find its own way down to the desired landing field on the surface of the destination planet without running afoul of any local authorities who might want to intercept this contraband cargo (or at least charge high tariffs on it).

I ended up spending some time flipping through my paperback copy of Dune afterwards, looking for references to exactly what the smugglers did with the quantities of spice which they managed to obtain on Arrakis. (Often buying it from the Fremen, who quite understandably preferred not to do business with the Harkonnens based in the cities near the north pole.)

As I recall, I didn't find anything in the text of Dune that proved my point beyond a shadow of a doubt -- but the flip side of this was I didn't spot anything that clearly demonstrated the truth of the other guy's interpretation, either. We see Gurney Halleck talking to smugglers, for instance, and we later learn he's been working for them nonstop for a couple of years (after he thought the Atreides family was extinct), until he suddenly bumps into Paul and his old loyalty reasserts itself. But we never saw any scenes describing exactly what a smuggling ship does after it leaves the surface of Arrakis with a bunch of melange stowed in a cargo hold.

One bit which caught my eye at the time, and I found it again just now, is a scene in which Lady Jessica is talking to Duke Leto about why she's invited Esmar Tuek, a well-known smuggler, to attend a formal dinner in the ducal palace that night. After she offers some reasons for why she and Thufir Hawat believe it will be a good idea to have him there, letting the other important guests see that Tuek is on good terms with the Duke, we get the following silent commentary:

And she thought: My darling, can't you see that this smuggler controls fast ships, that he can be bribed? We must have a way out, a door of escape from Arrakis if all else fails us here.

Twenty years ago I took this to mean that a hasty retreat via smuggling ship would be as independent a back door as Jessica thought she could find for her family -- even independent of the Spacing Guild and its mysterious agenda -- which was why she was buttering up a successful smuggler, instead of just trying to arrange a contingency plan with a local Guild representative. But I recognized then, and still do, that it is not crystal-clear just how far Jessica thought one of Tuek's "fast ships" could take a bunch of passengers while operating under its own power.

To clarify what I already know about the Dune Universe: I have read the six canonical novels which were written by Frank Herbert before he died, and I also own a copy of the non-canonical The Dune Encyclopedia. On the other hand, I have only tried to read one of the several "official" follow-up books which have been co-written by Brian Herbert (Frank's son) and Kevin J. Anderson. That was The Butlerian Jihad, soon after it was released. It totally failed to grab me, and I've never tried to read any of their other collaborations which are supposedly based on Frank Herbert's own notes about various aspects of the universe he had created.

So I'm asking: Does anyone know of solid evidence, in any "canonical" Dune book (whether written by Frank, or co-written by his son Brian), which provides a definitive answer to the question of whether or not big-time smugglers had the capability to move cargo from one solar system to another without relying upon the Spacing Guild to ferry them most of the way?

(Remember, I'm asking about what it was like in the period before Paul Muad'Dib became Emperor. He, and later his son Leto II, may have made all sorts of changes during their respective reigns!)