Thanks for the inputs. I have a centre fill vented cap, so can't see frunk filling up with vapors. Real 356s and 911s have fuse boxes next to tank. Guess it should be fine. Fuse box elsewhere will look neater though. Of course ease of access also important. Toying with the idea of mounting it on a tray which then gets attached below dash once done.
In other news, the driver side seat is in! (That'll be the right side seat to my American friends!) I faced an interesting dilemma - if the seat is mounted higher, fairly tall drivers will be comfortable. I hate it, however, when drivers looks like they are sitting on top of a speedster. I prefer my shoulder being flush with the top of the door. For this reason the seat is mounted pretty low. As things stand, I'm comfortable in the driving position with only about an inch of rearward travel still available. I'm 5ft 10. Shorter people will have no problem as there is plenty of travel.
Seeing that it is my car and not a commercial enterprise, I'll obviously keep it the way it is. But it does highlight a potential compromise for the manufacturers. If I ever sell (doubt it) to a taller person (statistically insignificant probability) then the solution would be to add half an inch for more travel. Or the hypothetical buyer can sit on the rear bench...