Mike,

PRE-Flight supports all the channels, not just two!
I'm flying it with a TX-to-gameport interface from MileHighWings:
www.milehighwings.com/joystick.htm#game
and it works just fine.

Configuring PRE-Flight to work with all 4 joystic axes ia a little tricky: the 4 proportional channels are Ch 01, 02, 06, and 07 (which is kinda strange).
Here'are the set-up instructions for PRE-Flight (at the bottom of the page):
http://www.milehighwings.com/manual.htm

Hope this helps,
Boris