60 litre fitted in my saloon spare wheel well, some pro's and cons with it, these tanks are more expensive than the larger cylinders, and with the smaller capacity you spend a bit more on petrol when the gas inevitably runs out.
But then you do keep your boot space, although i keep the spare loose in the boot obviously i can remove it and risk a puncture for full boot capacity.
Personally i fitted it because i need the through space to the back seats, so had to be a spare wheel well tank in my case.
I would encourage a cylinder if at all possible on grounds of cost and convenience. Donut range can give 250 to 170 miles depending on mood, but to get 250miles you need a 50mph contaflow along your entire journey or the patients of a dead man. HTH.
Ps, bare in mind the extra weight of the tank fitted, some members have had ride hight trouble fitting 100 or 90 litre cylinders iirc with standard suspension, but no need to worry if you have self levelling, possibly worth geometric set up after installation.