ATM 6" f/4 or not?

[Tom.Stock@gsbsc.gensig.com]

        I recently purchased a partially completed 6" mirror from a 
     friend.. apparently this being his first mirror, he thought he was 
     making an f/8 but actually made it f/4...it is almost completely 
     polished, but f/4 seems a little impractical for a 6" scope...
     
        Does anyone have any advice as to what I should do with this 
     mirror?
     
        The secondary would have to be a little over 2" for good 100" zone 
     illumination, which then causes vignetting of the 75% zone at the 
     eyepiece...
     
        This seems like a big obstruction for a 6"...I was thinking it 
     could make a good photographic scope however, except for the 
     vignetting at the eyepiece....
     
        I just hate regrinding this to f/6 or f/8 after seeing all of his 
     polishing efforts go into it...
     
     Oh, and there are a couple of scratches as well...
     
     
     -tom