1/8" from the wall is too short.
They do make a wall mount rated wax ring.Adjust waste horn to project 5/16" from
We use the foam rubber washer, and we test them before we leave the job. Even with the glue.
I used to work in a bicycle shop, and it looks like the same stuff I patched inner tubes with.
Oatey reinforced wax ring spec
We have been replacing with the American Standard Glenwall.
Gerber now makes a replacement too in the Maxwell line.