Duke:
If someone who actually knows the answers for Enya engines doesn't answer, here's the answer for the FP/LA 25, which I think will come close:
3 ounce (an FP-20 takes about 2 1/2 ounces to complete the pattern on my S-1)
Yes
Dunno (probably yes)
Dunno (probably yes, but grab a 10-4 to try as well)
Probably. Maybe 12000.
A Hayes 3 ounce tank works great on my S-1 but does not fit between the wing and engine if it's stock and if it's mounted in front of the landing gear. Being nuts, I made a right-angle fitting to get fuel out of the tank and have it nestled up to the LG wire. A more sane approach would have been to either mount the tank so it sits on top of the LG and against the wing LE, or mount it on the left side of the fuselage just opposite of the motor.
Mounting it on the left side of the fuselage has been repeatedly and strongly recommended. I haven't done it because I don't want to stare at a tank for the whole flight -- I want the side of the fuselage that I see looking its best. I'll let you decide how reasonable and sane that attitude is when there's good reason to believe that you'll get better performance with the tank mounted the "ugly" way.
Particularly if it's a matter of getting a new plane into the air before the Fly-A-Thon, I think you can have a less than perfect installation now, and go back and do better later. Just make the dang thing work! Go back and make it all perfect over the winter!
(and post a picture someplace)