I have owned both the OS .46 FX & the TT .46 Pro (plus an OS .61 FX & a TT .61 Pro) & I have done numerous tach tests & flown many hrs with these engines. The .46 FX does not out power the TT Pro, nor does it outlast the TT Pro. The nickel liner coating on the TT is literally twice as thick as that on the OS, & liner peeling just isn't a TT problem, unlike the OS engines. The TT castings, machining & materials are every bit as good as the OS equivalents and the TT is noticeably easier to tune -- it seldom flames out, whereas my FX was an annoyance in that regard. In my current engine inventory there are, among other things, 5 TT .46 Pros, a TT .61 Pro & no OS engines of any description.

I have also owned an OS .40 LA & an OS .46 LA -- they ran OK (better than the FX), but unlike the FX, neither one could pull the skin off a grape, & the plastic bits broke &/or leaked. In my opinion they are not worth the price, but they last quite a while -- plenty long enough to identify a good replacement.