I have done them...but it is hard to keep the bar on my shoulders. In the summertime I sweat like a pig (just look at my pics) and the bar likes to slide a lot..lol.
yeah i can tell you sweat... it looks like someone dumped a gallon jug of water over your head... you could always just cover your entire body in anti-persperant, and deodorent, maybe that could help your "slippery" situation. Or you could roll around in a tub of chalk... just another one of my retarted ideas.