I'll secon the flange idea. $40 for a little peice of steel is an awful lot considering it costs almost nothing to make once you have the fitment. Seriously, if you find a way to make these cheaply, you can make some cash. My SSQV would be happy to volunteer for this, as I have not bought my flange yet. I'm a bit leery of having it serve as the test mule for your BOV though.