Download QuickClock Advanced and let it calibrate that stuff for you. Some phones can't handle much under stock voltage or over stock clock. Others can drop the voltage by 50% or more and overclock 50% or more. Your specific phone is going to be different than everyone else's, so you really should download an app that does all that stuff for you.
My phone goes down to 9vsel and up to 1562MHz. The three people I know with Droid Xs that tried had vastly different results. One wouldn't go over 1100MHz or under 23vsel. The other two were in the middle. You have to find out for yourself what works best for your phone.
I used quick clock advanced, then tweaked slightly to my tastes. I never use the other profiles, but if I did go with the high speed it calculated, my high slot is 1406 78
I am running Liberty 2.0.1 and use the following settings:
300 18v
600 37v
800 42v
1000 53v
Currently I am at 12+ hours with 80% battery left. I have had no reboots or FCs of any kind. Keep in mind that all Droids are different and using quickclock advanced can be easier to find your minimum settings, but I just experimented with various settings until I found one that kept it stable but quick.