I'd be tempted to keep Sibbald at LM/LW. He seemed to move infield more to form a 3, which allows Devlin & Mullin to attack down the right.
I think Kabia looks good, however it's a hell of a jump from 3-4 sub appearances to starting a cup final. It's a shame Forrest and Serrano haven't developed more of a partnership, I seem to remember them having a few good games earlier in the season.