Grip issues with Ginetta G40, help please

[pant shitter]

Currently slogging through a GT5 championship. I'm having constant issues with this car and keeping the back end from losing grip. I'm playing with a controller, all assists off except ABS. Already fiddled with various controller options, most other cars are fine, it's just this one that's having the issue.

The back end tends to go when coasting or braking even the slightest amount through a corner. Corners with elevation changes are the absolute worst. I've never been great at tuning, so I mostly leave it alone. If it sounds like there is a quick fix, please be specific in what you think I should adjust.

I can take an LMP1 car up and down the California highway, but Brands Hatch is kicking my ass in this stupid thing. Help.

[pant shitter]

Alright, well, I made the car drivable enough for Brands Hatch. Still not great, and still looking for any advice. However, here's what I did if you Googled your way here:

Lowered rear tire pressure a little bit (0.1Bar at a time), put the brake bias towards the front (brake first, then turn), and made the steering ratio slower.

A combination of these things made the car drivable enough to get me through the race.

[Blunts]

I found the setup at http://projectcarssetups.eu/#/viewsetup/310282206 to be a good starting point for tweaking. The G40J is a very predictable once you get the hang of its braking points.