Most of the threads on the engine point out that the TT .07 is an exception to that rule about displacement. Runs fine but no powerhouse. In this case adding displacement counteracts the unequal level of performance and you get a mild mannered throttled engine with decent but unexceptional 1/2A level power.

If the AP .061 runs and behaves well enough that you are comfortable using it, you'll have a throttled 1/2A but again offering no more performance than the Cox.

The Cox has simplicity and nostalgic appeal going for it. Fuel, prime, flip and go.. fly 'till it runs out, can be all kinds of fun.

Cost of fuel for a 1/2A is not much of an issue.