This is from Bud Weaver - Six Pack Solutions...
I do take out the screws. There is a couple of things you can try before you send them off. Get hold of some PB Blaster. Spray the things thoroughly and let it pool inside the screw bosses with the TB facing up overnight. Blow out the screw bosses with compressed air the following day and try to gingerly to unscrew them. If that is to no avail then they will have to be drilled out. You can usually do it with a 1/8" LEFT HAND spiral drill bit. The screws are 8-32 which is a #29 (.136") tap drill pilot and the 1/8" will not interfere with the minor diameter of the threads. This takes a bit of finesse because I usually have to "flatten" the boogered up screw slot with an end mill before I can center-spot the screw for drilling. 
If you are not comfortable doing that then hit me up and i will do it for you. It usually runs $50.00 to get them out. that is my flat shop rate charge for that service. I have custom jig fixturing here and a dedicated mill that I use for this purpose.