Frank,
First off...Australia rules. I love Bundi and cokes. I was there in 2000 for 6 months. Went all over eastern Australia, south island of NZ, Papua New Guinea and Fiji. I went to uni in Lismore, NSW about 30 minutes west of Byron Bay.
I am no expert, but when I switched to 1.45 pistons and the Kyosho springs from the 1.5 pistons and stock springs the car was 100% more dialed. It just soaks up the landings and bumps great. I think the smaller piston hole will provide a little more pack and not slap the chassis as much.
Before getting the Jammin Big Bores, I would try and wait for the new Hyper BB off of the Hyper ST. They are bigger than the Jammins. They already have the shocks ready, they are testing springs for the car.
I have no washer behind the upper link on the front end with the Kortz mod. It would take a heck of a hit to take the link off of the ball. I will say there is considerably more play in the front end with this mod, but not a big deal on the track.
I started with the stock 5,5,grease in diffs. It just did not feel right. So I tried 5,7,1 and it was so loose it wasn't funny. Went to 3,3,1 for this last race and it was much, much better. I didn't think it would accelerate too well with low center diff weight, but it was great.
I also run the new rear hubs with no inserts. No slop this way.