Ive got a gert big un. Leisure battery that can't remember if it's a 120 or a 110 but it's too big to fit in the LH side so the driving battery sits in the LH side and leisure in the RH side, it was done before I had the van. Still a bit of a bugger to get out though, have to remove the air filter.
I fretted tons before I finally decided to chop out the spare wheel cavity, but once it was done I got two 85AH batteris in side by side. Very neat. However after GRINDING the tin out I discovered the short rubber tube on the tank vent pipe, that's just behind it, had come adrift. Eek !
yes I got the elecsol one, it seems the be the shortest height for a 110Ah battery, other makes will be considerably lower capacity for the same hight