In reply to Tigger:
We're currently doing a group test on all-rounder packs in the 40L sort of ballpark - models that are good to climb with, or go out walking for a day, but also big and supportive enough to carry overnight gear if needed.
At least a couple of these are around 42-44 litres, which sounds like the sort of size you're after (you may end up carrying rope etc on the outside even still, but you have to draw the size line somewhere if you're also wanting to winter climb wearing it - and for me that'd probably be around 45 litres).
I'm 6' and I find most fixed length day packs are too short on me. Some are available in different sizes, and I guess there are a rare few that have adjustable length backs (none in the group test that I can think of).
Of the models I'm personally using, the Mountain Equipment Fang 42 (plus) is the best fit on me - I find it long enough for the hip belt to sit where it should and do its job properly (not the case for me with several other packs). It also offers a good combination of capacity, excess packing (floating lid, daisychains etc), support when heavily weighted, and still good to climb with. It'd be a very decent winter climbing pack for instance.