Not much progress lately, all my time has been taken up by other things
I installed an up-post next to the magnet to catch the ball as it comes around the left orbit
Was a bit nervous about the installation since this wasn't at all planned for, and I had to just eyeball the location, but luckily it did barely fit
The post itself is a bit smaller than the sleeve, but the sleeve itself is nearly touching the magnet, so I definitely can't really get much closer
Sadly, even with this set up, the magnet still couldn't grab the ball. In retrospect I should have just screwed a regular post in at this location and tested the magnet with that first. If I pushed the ball even 1/4" closer to the magnet, then the magnet had no trouble grabbing the ball, but with the ball leaning against the right wall, there was just slightly too much distance. I can't move the wall, since it's part of the shooter lane, and I can't move the magnet, since it has to be aligned to drop to the upper flipper.
Again, I wondered about having an exposed core, and whether that would be enough, but I didn't want to drill the playfield to find out. Before setting up some test cuts on my spare playfield, I decided to test out the best-case scenario: instead of an exposed core, just expose the whole magnet! I stuck the magnet under the lexan sheet on my test playfield, and ran some wires to test it:
No problem here. The magnet easily grabs the ball from at least 1-1.5" further than it does with 1/4" of plywood in the way. I'm now very curious how this compares with the large exposed cores Stern uses now, but still don't want to spend $50 to find out. Even that wouldn't be needed though, if I do end up going the route of just covering the entire playfield with a plastic sheet, which is looking more and more enticing as a solution to many of my issues.
The main problem right now is actually cutting the sheet. Circular holes shouldn't be a big issue, but I'm not sure how cleanly I can make the slots for the target banks. My biggest worry is all the star rollovers. I'd have to cut holes for each of them that align very well with the holes in the playfield, and then raise the rollovers up to be flush with the sheet. I'll need to practice some more with my spare material and see how cleanly and accurately I can make all these cuts. Long term I'd probably need to get this laser cut, but I haven't had any luck finding a place to get a cut this big made yet