Yeah I also feel like it’s not consistent for drift. The highest I got was 2.5. I also got 3.5 but that was for a flipper.
I will try experimenting with seam as you mentioned.
If you get a straight seam on your flipper there’s every chance that it actually swung a bit.
I bowl an arm ball that swings away from a right hander, there’s absolutely nothing wrong with having a flipper that swings a bit.