I don't know of anyone using one of our pipes on a P70, but I know the 54-size pipe has been used on P60s with success.

We used to recommend 25mm as the distance but as our engines became more powerful (the Wren 44 went from 7.5 pounds to 10, the 54 from 12 pounds to 15 or more) we found that the pipe had to be moved further away and now recommend 30mm.

Sara Parish
Wren Turbines