Stumbled onto forum searching web for advice. Want to frame out a kitchen sink window bump out. Window size is 4' x 3 1/2'. Bump out will be 6 inches. Header is already there from the six foot slider I removed. Framing question: Do I frame the inside of the rough window opening(cripples on up) with double 2x10's(flush with inside 2 x 4's ,protruding 6" outside) to my rough size, or is it ok to pancake and facenail 3 or 4 2 x 6's on to the perimeter of the window opening even with sill and jack studs on the exterior of the house? I have two foot soffits over hangs so water is not an issue. Just want to make sure I am framing it correctly. Pics would help

Thanks