Lew,
If your going fenderless, you might want to consider the trunk. I built mine to go between the trunk area and the back of the seat, standing up (holds 18 gals.) Fumes aren't a problem if you vent to the outside. I open trunk lid to fill up, but you can have a fuel door on the outside if you want. If you have fenders some people put tanks behind the running board splash aprons.
Later, Mark