Thanks MartinSR for your willingness to reply. We're both looking at this the same way. The building up of the bottom rail transforming it from a vent to a frame to receive the window has me a little concerned. I'm thinking that by raising the bottom opening..the look of the front may change a bit. Unsure now if it would be for the good or not. Additionally the look of the sides will change as well. The traditional visual proportions of the window opening and it's frame is something I'd like to maintain if possible.
I'll probally work the problem backward from deciding how I'll trim out the front (mimicing the traditional frame) it's mounting/fastening down and then the buildup/frame holding the glass and the sealing of the glass.
Thanks...If I get this figured out I'll try to put together a tech thread on it.
tech69....you added nothing to this conversation....good game!