It wil be 7cm away from the Transom.
But I have made a descicion
Ill chuck out the parts I have, and order a L shaped pipe, and a flange the goes straight out of the cylinder.
THen the pipoe can sit in its original position.
Have to order them next month.
Thanks for your help so far.
I have messed with tuned pipes on rc planes before, and I know that they suck when not "on the pipe"