How slippy should a tc02c slipper be?

[Monkeysmate]

I would be grateful of any advice as to how people set their slippers up... I'm aware that the slipper needs to slip before the diff, but other than that, I'm learning...
I was told to hold the car on the ground by the back wheels and set it so that the front nearly jumped when you blip the throttle...
However, on very low grip surfaces, I'm having trouble putting power down, and the car wants to spin round, as one of the rear wheels spins up.
Tightening the diff tends to alleviate this to an extent, but I'm not comfortable with tightening the diff much, as it's basically just mashing ballbearings into the washers.
Then someone else had shown me that they have their slipper way looser, so that they can turn it with their thumb when gripping the rear wheels... Mines tighter than that...
I'd be grateful of any advice people are able to offer.
Thank you.