I think that could possibly work OR be incredibly frustrating and never quite right - more likely the latter. It would also be a very hard resale. I’d also quite how well the saddle would hold up.
Is there a large city near you you could go to and hit up several tack stores? Sit in several saddles? Do trials with the store? If you go to a store that sells Prestige, you can have them take a picture of you in a Prestige saddle and then send that pic to Prestige - Prestige will then be able to tell you the flap and seat they recommend (extra long, extra forward, etc.,)