Hey - WM T-34 O.S 55 AX Macks Tuned exhaust 4.750 header length
10/8 apc 15,500 to 15,700 on the ground .
10/9 apc 15,200 to 15,000 on the ground
but both fully unloaded in the air , the engine sounds the same peaking
next week we will try a 10/10 but I belive that 10/9 is max