I just maddened a SM T-38 with no issues. CG at 108mm and you will be just fine. Positive angle never hurts but an accurate CG is best. I'm also planning on starting my build on my SM F-5 and will post thread. I plan on posting my 38 pics soon. One issue with both jets is the MLG not retracting far enough into the fuselage forcing the main gear doors to be cracked open just a bit with gear up.