QQ Somenzini's 100cc Python has a flat stab and elevator . . (I think his 200cc version did too?). See attached pics. Hope they are clear enough.

The elevators also appear to be not taperred much at all leaving a very 'blunt' trailing edge. Current trends with F3A Aeobatic/Pattern planes is to have VERY blunt trailing edges on all surfaces . . I have heard of up to 12mm (1/2") being used. This appears to soften the control around neutral, and I expect it would create extra drag . . a desirable feature in modern day pattern flying.

I think that if you build it as per the original full size, it would fly just fine.

Cheers, Jeff