The guys have summed it all up for you - get rid of the O rings in the links (all of them) and use the side dampers only. Rear droop is a tuning aid to get the car to turn in, but at West Kent with their grip you should be at 1mm or less.
Rear droop is a compromise between having the car able to cope with the bumps and getting the right weight transfer onto the front axle as you turn in. On bumpy track go to 1.5mm at both ends, but for flat tracks you should be at 1mm or less at both ends.
Remember to set rear droop with the body on. GT12 shells, even the lightweights, are quite heavy. You could set the droop on the bench and it then increases (and reduces ride height) when the body goes on. If you have a lightweight shell it's less of a problem. With a heavyweight shell set the rear at 4.5mm ride height with 0.5mm droop. With the heavy body on it will go to 4mm/1mm.
With the kit tyres no more than half the front tyres should have additive - the inside half. If you are using SXT then put plenty on as it evaporates quickly. When using Spider Grip then don't overdo it that is just a waste of additive. If you find the car is a bit grabby in the first few laps with Spider Blue switch back to SXT. When the grip is up go to Spider Green.
Get someone at West Kent to show you how to set the tweak with the coin drop method. If Luke Burley is there he'll clue you in. Without that test make sure that the rear springs are equally compressed - when the car is off the ground both springs are equally compressed on both sides.
You didn't say what grade tyres you are using. The kit tyres should work everywhere. When the grip comes up and the car seems to understeer a bit, move to 40 rears. To make the car a bit safer, switch to 50 fronts at the same time.
I don't know which class you drove before, so give these cars a bit of time to do their stuff. Don't pile into corners too fast as you will lose control of the front tyres and the car will not straighten up properly out of the corner. Slow in, fast out and hitting your apexes is the way to get the most from what is a heavy car on relatively skinny tyres.
Good luck, and I hope you get a good run at the weekend.
