Another option to the friction might be the installation of a Beartooth neoprene sleeve on the stock. I installed one sold by CSMC, more to prevent my salty sweat in thew summer from screwing up the wood any more than it already is, but it does provide a smidgen of padding that might help without raising your head any more than it already is
http://www.csmcspecials.com/Stock_Guard_p/e0175.htm