If I recall, the Super Combat Streak is full bodied fuselage. I have a Doodle Streak. It has an elongated profile fuselage and enlarged tail feathers. It is one of the smoothest planes to fly (.35 size/modern 25) which I have. I love it. It has a Magnum XL 25 on it. The wing is a preserved ARF wing. When the original fuselage started to wiggle out front, I put a whole new solid fuselage on it. The original ARF fuselage was built-up and only tolerated around 50 flights with the vibration of a Fox 35. I had read that with a Fox 35, that would happen at around 50 flights. With a combat streak front end that should not be a problem. The issue is extending the fuselage. Here are the dimensions I used:
Fuselage - 28 1/2 length from the extreme front to the rear up under the horizontal stab.
Elevator - 24 inch at back edge
Horizontal Stab - 23 inch at back edge
Rudder 5 1/2 at the trailing edge.
This worked well for me. Have fun!