I only had a 4mm gap to fill with spacers but didn’t like the idea of junk getting caught up in there so I, too made a spacer.
Mine is meant to replace the spacers you need to use due to mbs tolerance differences, not anything moon did.
I like the added benefit that it also keeps the V ring from slipping away from the case for any reason. Also doesn’t require any additional/longer hardware.
Where’s that spacer at? Oh, it’s just so perfectly fitted you probably didn’t even notice it 
It’s easily modifiable for whatever gap of spacers you need, Lmk what gap size if you want the file.