sliding motor mount?

[sawdust1]

Has anyone here ever built a sliding motor mount? I mounted my x axis with a spring tensioner, works great. I wish to mount my Y axis with a tensioner as well but cannot use the same mounting method.

I would like to build a mounting plate so that the motor has 1/4 inch of travel, this is way to much travel I realize. By milling the 5 holes that the motor mounts in, elongated, the motor can slide up and down but not side to side. Nor will it be able to twist. The risk is that the torque might overpower the tensioner and allow the teeth to skip. I have not had this skip happen on my X axis.

Has anyone here got a file of a motor mount with elongated holes?
I am doing this because I have noticed that as I manually push the head across the gantry it gets tight then loose then tight. I don't see how my rails or rack could be bent, but something is amiss.
David