Also b) it was a nightmare to try and pack in such a way that kept an oxygen bottle securely in place AND accessible.
NOTE … We came across a bit of an issue just recently with the Crux AK47 / AK57 (RT) – the RT standing for Roll Top. Yes it is pretty much fully waterproof when the RT is rolled but … a) when the pack is only partially filled the lid then flops around on the outside and was difficult to secure in a way that kept it firmly in place. There may well be a lot of items that you want to have in the lid which can make it surprisingly heavy. Personally when I have a partially filled main compartment I like to stuff the lid inside and cinch up the main compartment to keep the lid in place inside – and this isn’t possible with the RT. Also b) it was a nightmare to try and pack in such a way that kept an oxygen bottle securely in place AND accessible. There is a tendency for the roll top to kink the hose leading to your mask or alternatively you end up leaving the main compartment pretty much open … in which case there’s a tendency for the oxygen bottle to be flopping around (and even a possibility that it might slide out when you are doubled over and / or taking the sack off). Advice – I would highly recommend NOT bringing a RT (Roll Top) version of any rucksack.