I talked to a fabrication shop and got some 22" hrs steel cutouts . Nice 3/4 " circle . Then I stuck them in a worn 20" tire from a tire shop junk pile and bolted it through the sidewall just above the bead shoulder . I added a plywood facer and backer and legs to support a vertical deflection the ideal would of course be down . With so many 20-22" LT tires available a nice 8 ply would be better than the HS rated 4 ply I used . The tire selected was about 10-12 " wide .
On reflection filled with rubber would be wise .
As a note on capture rounds approaching 950ftlb and above will punch through 1/4" hot rolled with a 1/2 plywood in front . The Facer stopped all of the splash . Mulch will be added to the new ones after my move to add more deceleration and lower deflection risks . The life span wasn't good on the 1/4 but the 3/4 held up well .