I have heard anecdotaly that the TT Pro 46 and the OS 46 FX (predecessor to the AX) were actually designed by the same person. I've got two TT Pro 46s and a TT GP 61. All three engines are keepers. I also have the 46 LA mounted on a Nexstar. Its slightly underpowered, but with an 11X5 prop, it has no problem pulling the Nexstar off a grass field.

Brad