they sound like ace mates kayak.
i had to buy a smaller pump to fit in mine TBF, and I typically carry a montane windproof.
also arm warmers, a largeish packet of nuts, regular toolkit i imagine anyone would carry ( chain breaker, mech hanger, multitool etc etc. ), spare tube, tubeless repair kit, phone, buff, gps.
there’s room in there for front/rear lights, another spare tube if i wanted, and i could switch out the windproof for a waterproof if i wanted to ( but typically I use a softshell if the temperature has got low, so the windproof will work with that if it’s that bad and I’m out in it ).
one bottle either side, and the only thing that bothers me a little is water capacity, but I did some pretty long days in the borders this year and didn’t run out of water.
so, yeah, you have to adapt a little ( shorter pump ), but i imagine if you’re the sort that’s going to leave home without a pump or enough water you can probably find an excuse to do that irrespective of your chosen portage method. 😉