Yeah my tunes are pretty on the nose through the corners.
If you are looking for stability here are the most common fixes in order of what I'd get rid of first:
I tend to run my ballast as rearward as possible to make the car rotate aggressively on corner entry, however it gets pretty wild at times. If you are having issues getting to the apex cleanly move the ballast forward until the car settles down. 50:50 weight balance is pretty safe in most cases, I prefer 49:51 and rarely venture out to 48:52 unless the car feels like it is on rails, which Super GT and JGTC cars are for me.
If the rear spring is anything other than minimum available I've actively added it there to decrease understeer/induce more oversteer through the corner exit. This may not be ideal for you, so reduce it back to minimum. In cases where the front spring is HIGHER than Minimum, I'm trying to stop oversteer, so you might have to add more.
If I'm running a rear ride height lower than front ride height again I'm trying to reduce understeer and create some oversteer in the mid corner. Even it out (usually lower the front) to get things even so that the car will behave nicely as you get back towards throttle.
I try to run as little rear DF as I can, more top speed and more oversteer so its great for me. Adding downforce can give a car stability in mid corner, but also more drive traction out of corners. Usually there is nearly double the rear downforce available from minimum so you can greatly increase your rear grip if you don't mind losing a few km/h.
If all else fails, add rear toe until the car calms down. It is the least elegant solution as it generates understeer in all handling conditions (Entry, Mid, Exit) but sometimes you run out of solutions and have to just give up in order to make the car stable.
