Parametric Stop for Thin Rip Jig

Stop element for [PaperBots](https://www.thingiverse.com/paperbot/): [Table Saw Digital Thin Rip Jig](https://www.thingiverse.com/thing:3314929).

My tire gauge is 3 mm shorter than it sould be, so I redesigned the stop block and added an additional spacer to make it fit.

I also changed some tolerances, so it fits a little bit easier into the base.