I use a 3/4 length underquilt which still requires a pad for my legs (feet to mid-thigh). I fold that smaller pad and place it as a backpanel in the pack.
BTW, Backpackinglight just did some comparative tests of frameless packs. They used the same pack and in one they put the pad in as a tube around the packs perimeter and in the other they folded the pad and placed it at the back panel. The folded pad in the back panel supported the pack more than the tube method.
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