Exactly what kind of testing have you done with those drives?
It's one thing to see a disk icon on Workbench, but have you tried opening a copy program and copying from a known working drive to the modded drive? Copy back the other way again? Formatting and filling the disk up?
Booting from a NDOS game floppy disk?
I have played about with lots of drives, and whilst I found lots that looked like they worked, after heavy testing I found some drives didn't really work exactly like an Amiga floppy drive should.
With the pin 2 <---> 34 swap in place, and the diode from DF1's Pin 1 RDY signal to (Pin 10?) on the cable, you can get a lot of drives to function. But only a few really fully work.
I was fiddling with one the other day, I could copy and delete files, I could insert disk see an icon and watch it disappear when I removed the disk and I could format, but if I opened a program like Xcopy, it would tell me that there was no disk in the drive. Wouldn't matter what I did.
A better solution I believe is this...
http://www.ianstedman.co.uk/Downloads/downloads.htmllook at amega.jpg and amega2.jpg.
I havn't tried yet myself, but I'm going to soon.