Its not really been a problem for me but I do see other struggling with it...
If you screw the DCT onto a battery a little too tight it can be a bit of a pain to get off, I think this could easily be rectified by making the flange plate of the carto with a flat edge, a D shape if you like, make the end cap of the DCT with a D shaped recess and problem solved as the flat edges would bite together and you'd be able to twist the tank itself to unscrew it, possibly wouldn't work as well if the o-rings were worn but I think it might be worth a look?
Just a thought

Speaking of o-rings, whats the latest news on getting spares?