here... what id id was just bought a 3" and 4" disc from usp (had to sand down the 3" a tad to get it to fir tho was way to tight) and then i glued it onto the 4" (with acrylic glue) and then glued it onto the tube first using a jig saw to cut it close and then sanded it all down smooth it turned out nice. but this one i tried to use CPVC cement and it cracked a bit. so i bought acrylic glue and that worked like a charm.
im making some reses if anybodys interested in them mine are 3" ID 3 1/2" OD tho. (not flaming just giving tips on how to do it)
also this was taken before it was finish saded at the bottom.