If you have the QB fuselage kit, there is a gotcha to watch for with the cabin top install.
Check to make sure that ALL of the rivets in the fuselage sill, both horizontal AND vertical sections ARE FLUSH RIVETS.
My QB fuse came with AN470 button head rivets in the vertical sections of the aft sill, 7 on each side. This made fitting the cabin top difficult and would have resulted in very thin fiberglass sections had I not found the problem.
Replacing those 14 rivets was fairly easy as access was available. When the flush rivets were installed the cabin top fit much better. There were still areas where the flange gets razor thin.
The plans say to just sand off the flange to the radius but I think most people will agree that they had to go well into the radius to get the top to fit. Seems to me that the cabin top door should have been 1/4" smaller. Then the plans would have been correct and most of us would still have a fiberglass radius on the edge...