I recently had a kilt that was reduced from a 38" to a 36". It was done by the kilt maker, so I'm not sure if a competent tailor could do this adequately or not. The solution for me was to move the two side buckles, right side, and the single strap on the left. It fits great...can't even tell it was a 38." See the thread: "Help,Tightening up a Kilt." Barb Tewksbury chimes in.

As for the length, I haven't a clue there. Good luck!