SE and Fuel Tanks....
NO, NO, NO! Take the GP tank back; don't even open the POS! That's the one tank Performance Specialties specifically says not to use. Remember the major problems with them a few years back? Granted, The Empire may have fixed that, but why take a chance?
Yup, I used to run headers on all of my helos, but not anymore. They are useful for certain applications, but once I learned how to tune my mixture I didn't need them anymore. I am NOT saying you don't know how to adjust mixture...<G>
I fitted one in a H9 CAP 232/Saito 150 combination, due to the kit tank being crap (big surprise; NOT) and an odd-shaped tank compartment. I used a Dubro 16 ounce and Hayes 4 ounce plumbed side-by-side. Worked great.
It will work even better with the YS. I definitely had that option as Plan B in my SE, if the Sullivan round 10 ouncer hadn't worked out.
I don't think that DuBro is gonna fit without major surgery on the former. You don't want to remove very much wood there, as it provides a lot of support to the front of the fuselage. The problem is the wing tube; it is in the way. The corners of a 10 ounce square tank just won't clear at the angle needed to insert it in the hole.
Steve