Well did a another day of testing today and had some mixed results.
It was terrible engine wise because I spent almost an entire day too solve some problems on my MF/JP frankenstein engine which still aren't solved.

On the chassis side of things the day was great.
Builded some new dampers at home which I thought would suit the current conditions and they worked great, car had better traction and was a lot easier to control and was a lot faster.
Also moved some weight towards the front, front end was really good, combined with moving the rear ARB connection 2mm inward this pretty much solved the understeer on hard acceleration.

At the last 5 minutes of the day I decided to give my Capricorn Hard light tires a try, and man those tires are good.
I only did 12 laps with them so first 6 or so were used to bed them in since they came right of the truer, but after that the laptimes dropped 0.3 seconds compared to what I ran earlier that day with the GRP tires.
The last 6 laps were within 0.3 seconds of each other and the best one was only 0.2 seconds off my personal best. I trued the tires to 65mm in the rear and 62.5 in the front so this amazes me even more, can't wait to run them with 59-61 and some high grip situation's.
I could hold a much tighter line in the tight S bends and accelerate pretty much full throttle without the back stepping out.
Balance under braking was improved as well.

I think I never had such a huge increase in performance before, ordered 20 sets of them right away.
Would recommend everyone to give them a try, here in Europe they also are one of the cheaper tires available.