driver side play


I have a rivarossi 0-4-0 mechanism I'm using to power a hobbyline static model saddle tank loco.I replaced the cracked plastic frame spacer with fabricated brass ones the "same" width as the plastic one and the bottom cover plate that partially fits inside frame rails.After reassembly the drivers move side to side .100" causing crankpins on front driver to touch main rods and crossheads. Originally tension from the pickups was used to center drivers,I will make pickups for it after this clearance issue is resolved.
My question is what is the allowable/desirable minimum side to side movement of drivers in a frame,I will make longer frame spacers once I determine the length needed.I know these little engines waddle a little going down track so eliminating side movement in frame it should lessen this.