Since George Dasher admitted that he had a hard time getting over lips in a vertical caving situation ... sounded like it be a good new thread for discussion of ideas and methods on the how to's.
Basically in my own experience lips can be of all sorts of types. From the severe undercut where there's roughly 3-6 inches of rock that makes the lip underhang, to the straight wall type with a sharp almost 90 degree edge at the top.
Lips can be difficult to get up and over that is true. Still this is what we all should be practicing on top of the basic SRT maneuvers i.e. change-overs, knot-crossings, etc.
I recall reading in On Rope about various methods to get up and over lips/edges. One method I tried and found that it painfully didn't work at all. It was wedging your arm/elbow between the rope and rock and using that as a wedge to make it easier to put your handled ascender past the lip. Problem with that is that if you don't have your weight off the rope by some degree you're literally crushing your own arm with your own weight. Not a good idear.
Other methods included taking the top ascender off and reaching past the lip (above you) and re-clipping on to the rope. This is well and good provided that you're able to do this quickly and effectively and that the rope has some clearance for the rope-guide of the ascender to "hook" back onto.
With a Frog system I found that by raising my body/croll up high enough I can remove the hand ascender to perform the maneuver easily enough.
I also use my free hand to push my body away from the rock and at the same time slide the hand ascender up past the lip/edge in one quick series of movements. I have to remember to cock my leg that the foot-loop/ascender is on so I'm not defeating the purpose of trying to lift the hand ascender past the lip/edge. Once the ascender is past the edge then I can step down in the foot loop and stand which will bring my upper torso up past the lip and I can climb/crawl my way up and out of that drop.
It's one of the reasons I strongly encourage my students to rely 99% on their leg muscles to get them up the rope and just use their arms to maintain upright balance while climbing. Reserving arm strength helps a great deal in getting one's self up and over and out of tricky lip situations.
Any other ideas/ methods/comments?? This might be a fun (and ed-ew-kay-shun-nal) thread.