Since I know little to nothing about mapping, I decompiled a surf map I had lying around that was modified for TF2 and deleted the team spawns and placed a player spawn and a portal gun. I then had to use SourceMod to change sv_airaccelerate to 100, since it's not accessible by normal means in any of the orange box games.
It didn't work. I could ride down a ramp okay, its just that the physics having to do with friction and air control are way different, so I couldn't change my direction on a ramp, or fly through the air very well.
So, does anyone who knows more about the physics differences in portal have any ideas? Like maybe some other cvars that could be altered? I messed around with sv_accelerate a little, but that didn't help either.
I'll upload my converted map and post it here once it's done.
EDIT: Here it is, I screwed up where I put the player start so you have to noclip it in the beginning: http://forums.thinking.withportals.com/dload.php?action=file&file_id=193

she doesnt post in this neck of the woods