Hi , my manta ray project has the body bonded to the pan so no access to fit a standard tank. I bought a spun stainless 8 gallon ish one and fitted in the rear storage area behind the seats. It is all plumbed and has no leaks but I am getting a fuel smell, not all the time. It came with a black plastic threaded cap which I swapped for a billet ally one, looks loads better but still has a pastic thread which feels a bit Mickey Mouse and would I think be easy to cross threa if you weren't careful. I have not fitted a vent to the tank, as I can sometimes hear gas vapour escaping . Have tightened it more which helped but worry on a hot day whether it will pressurise. Or give airlock problems.  Anyone else using these tanks and any suggestions.

you will need a vent breather pipe that goes down under the body as the heavier fuel vapour from your tank will sink into the body tub may be with disastrous results in hot weather.
it does not need to be large diameter, a couple of mm internal will do down through the back body onto the road.

Worth putting a valve in line if the vent is anywhere near the fuel level when full or you will just lose fuel, very good (but expensive) ball bearing one available from Demon tweeks

Stating the obvious but with  the tank near the back make sure the outlet is as far from the exhaust and engine as possible

Good luck
Dave

I had one of those demon tweaks ones fail on me   

Trial Bike ball bearing ones seem to work just as well, and only cost a couple of quid

Good advice, thank you all, do I just drill the vent into the neck of the tank below the cap threads.?  The ball bearing bike vents are sprung one way ?