I agree. The tolerance between the Rail and the Barrel Nut should be reduced as much as possible so that there is a solid, wobble-free fit. Geissele manages to do it with their Modular HK Handguard, so it is entirely possible to do. Just because the Handguard is secured by a cross-pin doesn't mean that the fit between the inside of the Rail and the outside of the Barrel Nut cannot be tight.
In other news, I managed to fit a LAW Tactical Gen 3 Folding Buttstock Adapter to my Raven. I had to re-cut the Receiver Extension (Buffer Tube) threads on the Lower Receiver in order to be able to secure the Adapter to the Lower. I used 1' 3/16-16 HSS Tap purchased off of Amazon,ca for $63. This was quite a chore, as the existing threads were actually quite shallow and had to be cut deeper in order to accommodate standard-dimension parts. Come to think of it, even getting the Receiver Extension off of the Lower Receiver was a bit of work as well, requiring the use of a padded vice to hold the Extension while I twisted the Lower Receiver with my hands. Genuine elbow grease required! Now that I have re-cut the threads, everything including the factory Receiver Extension threads onto the Lower Receiver much more easily - as it should be. It should go without saying that none of this additional work should be necessary, but right now it is.
Once the threads were re-cut on the Lower Receiver, everything went together perfectly with the exception of the Extension Plug which extends the length of the Bolt Carrier by sliding into the rear of the Carrier. As it turns out, the proprietary Bolt Carrier of the Raven is too large for the Plug that comes with the Folder Adapter for 5.56mm Bolt Carriers. So I had to substitute a 7.62mm AR10 size Plug to fit in the uniquely-dimensioned rear of the Raven Bolt Carrier. Of course, it was too large and had to be reduced in diameter using a bench-top Belt-Sander, but once it was made to fit the Raven it functioned 100%. A bit of work, but definitely worth the effort for such a long firearm when it comes to storage and transport. Folding the Buttstock reduces the length of the package by close to a foot, which is substantial.