You didn't mention your pack weight, but reading your description (e.g. tarptent) -- I assume that it is somewhere between UL and L. I think your problem is not so much that a frameless pack isn't providing enough load carrying comfort -- but that your pack is sized or shaped wrong for you.

The above doesn't mean that you should now knee-jerk to the other end for a heavy pack as suggested above.

Stating the obvious, the trick is to find a pack that provides just the right comfort and fit. If you dislike the design of GG -- then I second the suggestion above for looking into ULA packs.