Apologies for the half naked pic, if you look closely you can see what’s left of a crayfish claws on the outline of the carps belly must have been painful trying to push that out .. I read a article way back in one of the carp mags and saw the picture of a carp on the mat that regurgitated two 2 inch carp. Cannibals as well
Carp are more predatory than most people think. At frog spawning time they soon switch on to mopping them up. I chatted to a pike angler on my local water and he caught the big common on a plug fair hooked in the mouth. I've heard of quite a few carp being caught on sprats. Carp have to chew their food to make it small enough to pass into it's digestive system and that would limit the size of fish it would take.
Crayfish are also fair game and I've caught a few chub on freelined crays. They have to be crushed and spat out and then taken in smaller chunks. Linear has it's fair share of crayfish and I'm sure the carp harvest them. One night on B1 they drove me mad and I was getting pulls all night and didn't hardly get a wink. I suspect the carp weren't in the swim and I should have moved but was too tired and didn't think about it at the time. The Cotswolds Water Park also have plenty, in fact one bloke makes a living by harvesting them.
I've been reading about bivvys lately and one which seems to get good reviews is the Tacklebox Long Top. Personally, I've never used one but it might be worth a look - it seems very lightweight stripped out. One plus I can think of is that the Tacklebox's customer service is top class.
Well this would appear to be the obvious choice
https://www.ebay.co.uk/itm/Sonik-SK-TEK-Xtractor-10ft-2-Rod-Sleeve-Holdall-Carp-Fishing-Retractable-Rod-Bag-/384152021072?mkcid=16&mkevt=1&_trksid=p2349624.m46890.l49286&mkrid=710-127635-2958-0