To the tarp idea, this is what I did this last summer with my walker.
Got a cheap 6'x4' tarp from Lowes. Walker gets full, spread tarp on street, dump clippings on, and then pick up tarp and dump in.
When the walker was full to the top, it was a PIA to lift tarp, but get three big handfulls real quick and put it in the truck, then tarp is light as a feather. Took me a few yards of struggling with it to figure this out, and boy did I feel like an idiot.
Dont dump a whole yards worth on a tarp, that would be impossible.
Was like a $6 fix, and IMO this was fast and effective. Im upgrading to a reg-cab truck with a dump body on the back. Found a few that I really like that have a 12'x8'x4' dump box on them. My 5' toyota tacoma bed got full and moutain-topped too fast last year, plus a bigger engine is a must for the 7x14' enclosed im going to get, and I dont want to mess up my baby (the taco) anymore than I have.
ANYWAYS, back on topic, I have been trying to figure out how I'm going to dump the clippings in when the truck box is taller than me. Any ideas?