Harald:

That 1/6 Cub is an excellent first scale job, and being so, it's a lot of work to build.

If you are careful on all the wood fitting in the forward part of the fuselage it will hold your Magnum 46 with no trouble, but I'd add some triangular stock on the inside corners anyway, and perhaps use a slightly thicker firewall.

Other than that, the airplane is plenty strong if you don't try to fly it like a rocket. And do remember the wing struts on this plane are structural, don't attempt to fly it without them.

The muffler is your choice, but unless you do some mods there's no room to use one with the can behind the engine, so a Pitts muffler will probably stick out too.

My covering choice on this plane is doped Koverall, but 21st Century and others have adhesive backed iron-on fabrics in many colors, and a lot of them don't have to be painted after application. But if you really want scale looks use the Koverall, or spend the bucks for Stits System covering and materials.

Enjoy it, I have my third ready to start on construction.

Third? Yep. Overpowered the first one, and pulled the firewall off. Sold the second a couple moves back.

Bill.