Re: Can I make the clutch slip a little?
One thing no one has mentioned here - If you have never driven a manual transmission car with a clutch you would not know it.
You must let out the clutch until you hit the engagement spot ("sweet spot" - different on every machine). Then move the pedal extremely slowly - feather the pedal - until it engages, then let out the clutch the rest of the way. If you don't do this, it doesn't matter what you do to the belts, it will jolt into gear. Belt drives are more touchy than an automotive clutch, but the same principle applies.
Also, "riding the clutch" - keeping the pedal just above this sweet spot will allow quick disengagement when approaching obstructions. Everything happens in that micro-space with a clutch. You shouldn't ride the clutch while mowing straight stretches though, because it will wear out clutch parts and belts prematurely.