I would say design of the pack both original and the silvermans type is very good, however , the frame is the problem, its really heavy, its made of steel and you will swear at the additional weight . if you like the style, go for US alice pack, similar design, aluminium frame! Big weight difference. I use medium and large alice packs sometimes, however again.. both designs are flawed as the packs weight distribution is laterally not vertically, so the pack pulls you backwards, hence pictures of troops leaning forward under the load, the cyclops or crusader or vulcan style based on mountain rucksacks stack the weight vitically and keep the load close to the body and its centre of gravity. Less back strain, better load placement on the hips due to waist belts, no hip belt on the alice or sas bergen worth the damn.
In short, its a beast, it will outlive you even when abused, but will keep your chiropractor topped up with beer tokens.