Ok - here's some pics ...

pic 1 - tank bay - 2 1/2" wide. A Sullivan 12 oz tank barely fits in the width
pic 2/3 - the wing bag - no pass thru of F2
pic 4 - measurin' stick
pic 5 - standard servos 3 abreast - not much room for servo arms, control rods or adjustment
pic 6 - throttle servo positioned ahead of the elevator / rudder servos
pic 7 - balsa-n-ply open face sandwich

Carl - I think you say to install rails laterally. I was thinking of using 1/4" balsa stock w/ 1/8" ply glued to the top of the balsa making 3/8 x 1/4 rails. I like the 1"x1"lite ply end plate idea. I just don't think that there's sufficient room to mount 3 servos side-by-side. I've got pretty fat fingers ...

Just may have to rethink use of slant nose Sullivan tank. That's what's pictured in the plans.