I use exactly the same angle meter! I find a bit annoying the 180 degrees measuring range... beacuse you'll end systematically further, both with the valve and the exhaust. So I have to be aware of that, specially for the exhaust: it's easy to read 178° when actually it's 182° !! It's very accurate, though.

Because of the hi sensitivity of the digital goniometer i cut a stripe from a thin sheet of paper and use it as a "stop". It's meaningless in the read, and basically acts just like your piston stopper.

I have to ask you 2 things:

1- How can I set the perfect BDC - TDC ? I'm having issues beacuse of the rod-play. Even with a new engine once you have sprayed it with motor cleaner you find at least 3° of play...

2- Which is the best method to make clear visible sign ( scratch? ) on the crank as a reference before dremel?

Thank you very much!!!