I had a pair of Kuhl Liberator convertible pants, but found them very baggy. I may just have really lanky legs. My Prana pants seem to have the best balance between relaxed fit without being baggy (though, all have cotton in them, which won't work).
I've tried Ex-Officio pants and found them VERY loose, which is exactly the problem I'm trying to avoid. Otherwise, I'd definitely go with them.
While posting this, I've also been window-shopping extensively. Right now, my front-runner is actually Prana's Men's Zion Stretch Convertible pants. Anyone have experience with these? They look like they'll work, but 13oz is about 4-5oz more than I wanted. I guess with zips and a belt, it won't necessarily translate to bulk.
This might be heresy on BPL, but bulk > weight for me in this case.
If you don't look good while drinking Switchback in Burlington, go home....