I think 600kg is too heavy for a bug, but apart from that, you'll have a problem towing anything with a slammed car. All the decent tow bars for bugs reach under the engine and gearbox, so if ground clearance is minimal you're best sticking with a tent.
There's always Ratty Black Bug Dude's solution! (blatantly nicked from Orange912's photobucket!)
Or mine if you raise your car a bit:
Combi-camp trailer tents are just the best things ever! Ours is an Easy, which is so light (
350kg)I can tow it with my bug, and it doesn't need brakes fitted. Best thing is, you undo one clip, fold out the top and you're ready to get a brew on before everyone else has got their tents out their bags! (ok, the awning takes a bit longer but you don't need that really)
They're on ebay for anything between £100 and £500 depending on age and spec.