Here is the result of testing and tuning on my b4.1 worlds with big bores. This setup uses softer springs than the common 'team' setups and instead relies on roll center modifications and a reduction in standard rear ride height to great a balance of roll and front/rear weight transfer. I used this setup to TQ and place 2nd in Saturday's local club racing. I was very pleased with the car all night.

Pistons
The big bores with 1.6 pistons and the same weight oil have less damping but more pack when compared to the old shocks. You can see this yourself by bolting an old and new shock together at the eyelet and just playing with them. If you go up a half weight in oil, the 1.6 have more damping than the old shocks period, both normal damping and pack. You can run the 1.7s with thicker oil and get basically the same regular damping speed and pack as the old small bore shocks, but then what's the point of going to big bores if you can't get more pack for big jumps paired with lighter initial damping to float over bumps better.

More roll with 1.6 pistons
The lighter damping causes the car to roll quite a bit more than with the old shock setups. This is immediately apparent when you try to run brown front springs and black rear springs, basically the old shock spring rates (old rear green == new rear black). In my testing and tuning, I determined that at 24mm ride height, even with a shaved u-brace w/ no washers and the a-hubs, which offer a higher roll center than the c-hubs, I could not keep the rear from rolling too much and washing out in the rear at times, especially when coming out of corners.

Chasing the rear with stiffer springs for roll, then the front with stiffer springs for traction.
I went to the green rear springs, which allowed me to get the rear roll center dialed in, but unfortunately made the rear very eager to break free under braking and corner entry. I went to black front springs to compensate for this and was pretty happy with the black front / green rear combo all around once I got roll centers dialed back in via ball stud washer tuning, however the car just seemed to be, outside of a lack of chassis slapping, not quite as good as it was with the old shocks. I did manage to do well with it in club racing (a previous night), but It had both less traction and steering than my small bore setup. It felt plush, but it was less capable than my old small bore setup.

Lower the rear
Lowering the rear to 23mm and pairing it with the black springs in the rear with browns in the front was the sweet spot. The front/rear weight transfer difference due to lowering the rear was easily canceled out by the slightly stiffer green rear spring (which is one stiffer than the old green spring). The rear roll center needed fixing after the change in rear ride height, but one washer got the job done nicely, ending at 2 washers on a shaved u-brace with the a-hubs.

The front roll center
The front, after going back down to brown springs, needed some love as it was flopping over in hard sweeper corners. I found that going down about one washer there from my old small bore setup was about right, leaving me with one washer up front. Zero washers was very direct and felt good, but provided me with far more steering than I needed where as one washer made the car very forgiving and neutral on our high speed sections. 1/0 front washers will definitely be a tuning point for me in the future depending on track layout.

Wayne