Issues mounting Nikkor-w 300/5.6 in Toyo field lensboard

Trying to mount a Nikkor-w 300/5.6 in a Toyo field lensboard, and I'm running into two issues.

Issue 1 - What are the 4 small holes drilled into the lensboard and how do I plug them?

Issue 2 - I cannot get the lock ring to actually do its job. I'm a LF newb, so I may be doing something wrong here ... I separated the front and rear elements and put the front element down. I then put the lensboard over the front element and tried to tighten the lock ring. It tightens, but due to its shape (like a top hat), the lens is not actually secured to the lensboard.

I have some boards that were drilled so that solenoids could be attached. I cover the holes with darkroom tape. Electrical tape will do too.

Try turning the retaining ring over.

Thanks Dan!

Black silicone rubber for filling the drilled mount holes. For a permanent fill use JB Weld. Tape is fine for a temporary patch. +1 for turn the retainer ring over.

It is hard to tell form the pictures, but there is something fishy about the hole in the lensboad. It looks to small or out of round, the locking ring has a little shoulder on it and that what sits in to the board.You might have the wrong locking ring maybe.