Jett FIRE 50 users.. what kind of rpms are you getting?
My buddy Joe has a DD with a piped Jett FIRE 50 that we tached at 18,500 on an APC 9x8. 15% Mach 7 fuel, K&B 1L plug. My ST GS45 with a homemade mousse can pipe (MCP) turned this same prop at 16,500.
For fun, we replaced the Macs pipe with the MCP on the Jett 50 and got the exact same 18,500 RPM. That blew us away! But we never tried flying the MCP on the DD.