So far as I know, credit for the idea of using an inclinometer goes to Scooter Republic, the Buzzwangle inventors.
Now a decent inclinometer is pretty cheap, like $25 on Amazon. But the CNC'ed attachment tool they provide, along with the piston stop, which is redundant for me, made it hard to justify the cost.
What I did instead is tape a neodymium magnet to the back of my inclinometer, stick that to the flywheel, and do it that way.
For whatever reason, I decided to work this out to deal with checking the Sprint's timing over the weekend and once I sorted it, the entire process took about two minutes, plus no messing with attaching paperclips to the cases, sucking my printed degree wheel into the flywheel (yeah, I've done that before), or any other complexity. And as an added bonus, the arithmetic is easier, too.
Here's my specific technique, with pictures, and happy timing, everyone!