Its the opposite. The situation has nothing to do with diff, its a f/r grip balance, at high speed. The front is not the issue, the rear is. I noticed on the initial setup, Cseils mentions he is running -3 deg rear camber, I feel this is way too much. Id be more around the 1.5-2 deg mark. I would bet that the tire is still running on the inside of the tread when its in the middle of the corner, and with it being a FWD car, with very little weight in the rear, the car doesn't have the rear weight to push into the outside tire, and push the tread over, to hit the full width of the tread onto the racing surface. Basically its skating over the surface with the inside of the tread, instead of rolling onto the full width of the tread.

This is why we start with neg camber. If you run your tires with 0 deg camber, the tire will roll off the tread onto the outside while corning fast. We start the tire with neg camber, to allow the full width of the tire to contact the surface (giving max grip) when the car has fully transfer weight to the outside, and the spring had compressed and the car is generating max grip in the middle of a corner.

When I say "the tire will roll" Ill explain what is happening here. Your car enters the corner, the outside tires are providing grip to enable you to change the direction (turn). What happens in a high speed sweeper, is the car requires the most grip in order to change direction (turn). As the car starts to turn, the tire grips, and now while the weight of the car wants to travel straight, the tires act against this travel, and the resulting force on the tire tread is what makes the tire roll. Now you can see from this explanation, that more weight is actually a good thing here to provide more tire roll. The more weight, the easier it is to roll the tire onto the tread. So a heaver car, you will use more camber, so u don't roll the tire too much, and off the tread. But this situation on the rear of a FWD mini, you don't have enough weight to make the tire roll onto the tread, when you start with -3 deg camber. Itll take a lot of force to make it roll that much, and the mini simply doesn't have enough weight to transfer into inertia, to make the tire roll from -3 deg to make the tread flat on the racing surface.

I've kept the explanation there purely to the static camber, the weight and the roll of the tire and tread. You can really really confuse the situation when you include things like side wall stiffness, camber gain, raising/lowering COG etc etc. Something I definitely wont do on here Hope that helps and kinda made sense lol