I used Carl's suggestion and built lite ply end mounting plates. The servo rails are made out of 1/4" balsa sheet laminated with 1/8" air ply on top. Aband saw was used to cut the individual rails.

pic 1 - 1/8" lite ply with 1/4 x 3/8 rail holes
pic 2 - 1/4" balsa / 1/8" ply laminate
pic 3 - componets
pic 4 - just gotta remember to put the ply on top
pic 5 - with standard servo