stock 46
16.6k sounds pretty good on a 9x7, especially on 5%. I would expect the stock TH to turn 500 to 1000 rpms less than what it could with a Perf. Spec. pipe. Yours and Cy's numbers suggest that the TH and TT are close in power.
What is your 4 lb model? Depending on the airframe, there may be a better prop than a 9x7 for all out speed.
Paul