I had a ST 45X FIRE in a modified DC RC Doddger Q-500 (39"wing and v-tail with no landing gear) for about a year. The ST runs simular to a K&B 6.5 FIRE - 16,500 static with APC 8-10 and unloads a lot in the air. Use a MACS standard 7.5 cc pipe not a nitro pipe and 15% fuel. MACS also makes headers for the ST 45X even though they are'nt listed in their catalog @www.macspro.com so you will have to call MACS to see if he has any in stock and if he does'nt go to
www.sheldonshobbies.com they have almost every header MACS makes and they are also less expensive. You will have to call sheldons because they doe'nt list all items on their web site. BTW I know they have ST 45X headers because I was down there two weeks ago and they a box full in the stock room. You will need to know which style you need-0 degree 15 degree or fuse top. I hope this info helps you.