Well I've done it now too. Clamped the plate to a board, and used a jig-saw to slice 1/4" off the bottom, and 3/4" off the top of the plate. Purchased some stainless bolts, wingnuts, and rubber isolators.

The plate ended up sitting 1/8" or so from the lower chin because that's as low in the grill as I could get the bolt holes to line up... Might not have needed to trim the bottom...

I also drilled to upper holes ever so slightly too high on the plate, so they didn't line up with an opening in the mesh...

Usingly only the lower bolts it feels rather secure, so I don't think I'm going to worry about it...