DADS50,
in photo (A), it looks like it could be touching the rib on the back but there is a "blob" of plastic on the back of the Reducer that kept it off.
Also (with ign key On) I pulled on the Reducer a bit to confirm it was not touching and there was no movement of the Needle.

Once I confirmed that, I had to jus' keep "messing with it".....and broke it. (can't leave good enough alone)
So I ordered another Voltage Reducer.

you posted......Im a little confused on your second test where it went to 3/8
Compared to when it went to full

? just to re-affirm, 3/8 full is with it all wired up.
Full is with Sender Flange wire disconnected.

I watched your YouTube video, very nice tribute.

Jim