Shimming the gear box

[Mori63]

Hi ,I'm having a nightmare trying to shim the gearbox. The shaft sits below the gearbox as it should do and I can get it all shimmed up nicely until I put it in 1st ,then the sliding dog protrudes out of the end shaft pushing the shim on to the endplate.ive tried various combinations of shafts and dogs but protrudes to some extent.my question is would it be ok to file the ends of the dog down until sits flush with the shim recess on he 1st gear.thanks.

[dave411]

Should it be shimmed in neutral?