If by "aft" top skin you mean the one aft of the one Bob mentioned... some do and some don't. I don't think it would affect the rigidity much for storage purposes. Certainly the forward-most top skin on the tailcone needs to stay off until after you attach the cabin cover. I forget what they refer to each one as in the plans.
We riveted our "aft" skin on in sequence with the plans (where it sounds like you are now) and don't regret it-- however installing things like the seat belt attach cables and the magnetometer mount were a bit of a PITA. I had an especially bad experience though because I swapped out with stainless bolts at a later time and had some galling problems, so instead of doing it once I had to do it the equivalent of like 3-4 times, with the middle experiences being particularly frustrating. That's all behind us now though
On the other hand, if you leave it un-riveted, you'll need to slither in there at some future time and rivet it on, which in my opinion would be almost as difficult as (if not harder than) the other tasks you made easier on yourself by leaving it off. So I guess it's a 50-50 in my opinion.
Small tangent, still tailcone parts but much later in the build: One thing I would definitely leave off if we did this again is that darn baggage bulkhead channel. When you get to section 33-8 Step 4, riveting the F-1028 baggage bulkhead channel to the F-1029R bellcrank rib, I'd recommend just leaving it cleco'ed. It's just 4 rivets and you can do them at a much later point (like right when you go to attach the cabin top). If you're even slightly horizontally challenged like me, you'll benefit from the increased slither room when doing things in the tailcone.
Good luck! -Mike
__________________
Mike Jimenez & Sarah Hammonds
EAA Chapter 33 Prez & Soc Chair
Marion, IA USA
RV-10 In progress! (N165MJ reserved)
-Emp & Wings complete
-Panel wired up, working on Fuse & Finish
-Blog horribly outdated (sorry)
-Too many distractions, we will finish the plane someday!!!
http://mikeandsarahrv10.blogspot.com/
http://www.eaa33.org/