ATM 8.5" candle mirror update and help!!!

[Viper71049@aol.com]

Hello All,
 
 Since my grinding machine is complete and I got my 8.5" Cassegrain Telescope 
design made, I need help on the mirror. I dont need help on grinding or 
polishing I need help on how to remove a rim on the bottom side of the 
mirror. I will explain..
 
 It is a 8.5" mirror with a 3/4" wide rim and about 3/4" deep. Think of the 
mirror as a 7/8" thick flat mirror with a rim on the bottom 3/4" wide and 
3/4" thick. The question is I want this mirror as good as possible and looks 
good too. How can i remove this "rim"? 
 
 Drawing below, Cross Section Side View... 
           
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 How can I remove this "RIM" and any Ideas? I would think this would cause 
the center to sag and the edge to be normal......
 
 Tony