Hey, Keith!
1.) keeping them flat w/ plywood, framing, etc.
• What MJ said works for me, too ... but I've also found that properly installed T-Molding can help minimize post-instalation door warpage.
2.) Door jam trim - like aluminum "z" channel, etc.
• KISS - simple aluminum Edge Molding* ... with 1" T-Molding* on the door and a good weather/Door Seal*, you don't need an inside "jamb"
3.) Space around door.
• I've been using 1/4" all 'round the door except at the hinge, where I increase it to 3/8" (
before any trim goes on), and have had no clearance problems.
4.) Hinges, seals, etc.
• While I state that my custom-formed Offset Door Hinges* will only fit doors/walls 1" thick or less, I can probably squeeze another 1/16" out for you ...

...! As mentioned above, I've got Door Seal*, too ...
*
http://www.teardrops.net/LilBear/parts.html
Give me a holler ... happy to help any way I can ...
[email protected]
Good Luck however you choose to go! and as always ...
CHEERS!
Grant
Celebrating
Retirement after over
32 Years of Building, Promoting, Supporting, Supplying, Living the Lifestyle, and Loving
Teardrop Trailers!"Life Moves a Little Slower When You're On Teardrop Time"The nature of Life, itself, is change ...
"Those who matter, don't mind, and those who mind, don't matter." 