What springs do you have on the car,and have you had the diff to bits,cleaned it and re oiled it?. Do you know what thickness oil is in the diff?. I run 10,000wt in mine on carpet.
I would say the holes in the Pistons would be ok. I run mine with the six hole Pistons in with two drilled to 1.4mm.
Standard hole size is 1.2mm I think.
You also need higher thickness oil in the front shocks than the rear as has been said before.
Phill