Issue installing Elftmann Pro match trigger

Got an Elftmann match pro trigger for the M4-22. Unfortunately, it won't install.

On the match pro install video it says that if the front part of your receiver isn't cleared to fit the washers for the trigger housing screws, you can't use our system.

On my Tippman (>21K serial), the Elftmann washer fits perfectly on the left side of the receiver where there's a half-round cutout. On the right side of the receiver, the cutout looks like the same but the Elftmann washer will not fit into that half round cutout, it won't lie flat. I've reached out to Elftmann but they're closed weekends.

Anyone run into this, and if so how did you work around?

ETA: A workaround, not thrilled but it works. For the washer on the side that wouldn't fit, I tried all 4 of the washers from the other trigger housing screws, none fit. So I think the Tippmann receiver is slightly out of spec on the half-round cutout on the right side. I dremeled a slight bit off the washer at about 1:00 to 2:00 as in the pic, making it able to slip into the half-round cutout and lie flat.