A while ago while cycling through Eugene, Oregon I stopped at a bike shop and saw that they had two Schwalbe Marathons. When I asked the shop owner the price he said, "Ugg, those things are a bear to mount on a rim. You can have 'em for $20 a piece."
So, don't feel bad. They are a real chore to get on. If all else fails, use four hands and grease the last bit to get it over the edge.
Fortunately, once on the tires rarely flat... but be prepared for a few angry words if they do.