If I were you I would run the .25 instead of the .15 for your first combat plane. You will likely build heavy and the .25 can handle weight better. I can use all full size gear in my 25 size planes and end up around 3.25 .lbs. My 15 (ssc) planes with all full size gear end up close to 3 and fly kinda sluggish . The 25 planes in my opinion are just more enjoyable to fly with the added power. Also it seems that the .25s are less finicky than the 15s.
I've built a few 25s that ended up around 3.75 pounds and still flew nicely