[Tom Line]

I would consider changing the location of your digital encoder for a couple reasons.

First, as you tension the belt by moving your cim, it will change the engagement on the Digital encoder.
Secondly, generally speaking those things don't appreciate a lot of side-loading.
Third, if your belt slips, your wheel will no longer be aligned with the encoder reading.

I'd consider a small lightweight bracket that places it directly over the primary shaft of the module itself, so you'll always know the true position of the module. This also relieves any side-pressure on it, and it can be coupled with something as simple as surgical tubing. It will probably be a wash weight-wise.