Your reference to #5 and #10 blades make me think you're using something similiar to an A-5 clipper with snap-on blades? Really not truly a body clipper? Which is a good way to ruin an expensive pair of clippers. What you need, even to do a trace clip on a full coated horse, is something like this:
Dover Saddlery | Oster Variable Speed Clipmaster Horse Clipper .
The important feature is the adjustable tension on the blades.