If the head isn't completely rounded out, you might try taking some JB Weld, filling the hole in flush, then inserting a Torx (star) bit, or allen wrench in it, and let it sit overnight. Might harden enough that you can then turn the screw out. I've used this method before on several things, and it's worked well. Just file/sand/scrape the bit clean when you are done.
2006 Rytera Bullet X 60#---2008 Moab 70#
2008/12 Firecat 60#--- 2010 Warthog 70#
2010/2012 Alien X 65# 2011 Onzas 60 & 70#
2009 Warthog 70#---2009 Firehawk 70#
2010 Strother SR-71 65# & 2012 Strother Rush 65#
I hunt, therefore I eat. lol