That's a tricky situation with the Koetsu! I remember struggling with effective mass on a different tonearm once. While I don't know the FatBoy specifically, you could try adding a heavier headshell or even experimenting with strategically placed damping materials. It might sound silly, but when I'm pulling my hair out with audio stuff, sometimes I just need a break and play the Dinosaur Game to clear my head. Good luck finding the right solution!

Okay, I checked out the Accelerometer Results! Very interesting. I've been playing around with similar data for a pet project tracking my dog's activity. One thing I found really helped filter out noise was smoothing the data with a rolling average. It made the patterns much clearer. Speaking of activity, have you ever heard of Eggy Car? It's a physics-based game where you drive an egg... surprisingly engaging! Anyway, looking forward to seeing what you all come up with.