My router plate, and table, are both homemade. I have no movement at alll - my plate is not square, rather a sort of odd shape, which does tend to lock it in place. But if it did move, I would just place a small shim, or two, in the crack, and not worry about it.
"It ain't what you're told, it's what you know." - Granny Weatherwax
Gather the villagers, pitchforks, torches; we march at dusk!
Some days, the supply of available curse words is insufficient to meet my demands.
.....Call me a craftsman, artisan, or artistic, and I will accept that. Call me an artist and you will likely get a quite rude comment in return. I am not a @#$%ing artist.