I agree and disagree with you there FGYT, they are massive but you just have to use the side compression straps to manage the c o g, i find them very comfy over long distance, i have a long back and i suggest that as with all pack you should try a get to a shop to try it, just because you can get them reletivly cheaply dosent mean you shouldn't put the same concidaration into the purchase, take some kit with you to load up the ruck to get a feel for how it sits, if you want know the difference, a short back will sit squarly across your shoulders and will give you a very bad carry posture, where as the long back will sit like most other pack, neither have any sort of air gap between you or the pack, so sweaty backs are all ways a concideration, the internal frame is made up of four ally bars with one across the top and three hanging verticaly, and with a bit of pressure can be moulded to your shape.I hope tis is making sense. cheers Southey.