Mike I have never used tuning plates for the simple reason that I like my baffle plate setup. But Yes you could do exactly what you are talking about and go reverse flow or tuning plate mode. I am going to offer this style of cooker on my website that will be online very soon
I use tuning plates, I don't need to adjust them very often as they work great as a RF style when closed up. It seems to me that the bevel you are speaking of will really only be more work for the one making them. They don't leak anything to speak of if they are just cut straight anyway.
Just my $0.02
Current Smokers: Backyard RF Offset and Hybrid RF Offset trailer rig with Cowboy cooker and fish fryer, always room for more........
If time permits today I'm going to grab the steel plate at a local scrap yard. They rebuild/modify alot of ships in the Miami port area. I'm told they have 1/4" coming in. Good score if it is. Just hope its not to thick.
Should my Baffle plate slope up away from FB end? I think I read 1"????