It seems like this should be easier than it is, but finding pants to practice in is like mission impossible for me. (And it could be that I am just real picky...)
Have a bunch of Be Present pants that work well. However, the waist tends to roll up onto itself, leaving me a bit, exposed in some poses. (I have always had "muffin tops" regardless of body weight and fat %, and this could be an issue?)
So, now that I have shared probably too much information, any suggestions for some light weight, easy to move in, stay on the waist pants for a Pilates man?

(Where is that much needed edit button?) :)
I forgot to mention that this comes on the heel of trying 3 new pants:
Prana's Zion Stretch - These seem like they will work. Only concern is that with the weight of the fabric, it may be like practicing "Bikram" Pilates. That sort of goes against the "Don't let them see you sweat" thing.
Prana's Momentum - Kept thinking of Anya's "Sail Away" while trying these on. Not for me. And also there is that waist issue.
Zobha's Essentials - Same as with the Momentum. Plus, very heavy fabric.
Okay, edit is done.

Whatever you wear, make sure the material is cool and you are able to move properly in it. i.e. the material needs some give. It is also better to wear clothes that fit to the body so you and your instructor are better able to observe your posture. Lycra running gear's a good choice! Whatever you do, do not wear sports shorts with the safety net inside! They can restrict your movement and put your anatomy on show! The safety net doesn't always stop your bits escaping... I speak from experience as a teacher who has seen these bits on display! ;)

Have you tried Lululemon Pants in2sight? They seem to work well for men (particularly the shorts which often have a sort of lightweight bike short within) to prevent the worry of exposure during certain exercises.