XRAY RACER,
I run a Pro 4 with the same deck/top deck set up you mentioned on rubber tires.
I have found that by running a very soft set up I get unbelievable traction and steering.
I use 30 wgt oil in all shocks, 4.5-5.0 mm ride height (smooth track) medium front spring and very soft rear spring (couldn't tell you the rates as I dont know myself, sorry) 1mm droop rear, 1.5mm droop front, double shims on front upper linkages, Outer hole lower arm and second outer hole bulkhead front, second outer hole lower arm and inner hole bulkhead rear.1 deg toe out front and using the 3 degree toe in block rear. Neutral kick up and anti dive (standard factory settings)
At the moment Im using Sorex 28R no addatives or warmers. Stratus 3.0 body
I must say that the above set up is for a very smooth track and at this time I'm running 540 and Stock. I have used this set up with an extra .5mm added to the ride height for a rough but high grip track and it worked a charm.
I too race an Xray and I must say, the Pro 4 with this set up has been out cornering and out manouvering my competition but i have been struggling with gear ratios a little.
If you start at this point I'm sure you will find the car very fast and with minor adjustments to suit your driving style, you could be resting the Xray for a while.
I have been racing shaft cars for just over 1.5 years now and just started racing a belt car to see what all the fuss is. It is really important that you drive the car as smoothly as possible when it come to throttle. A shaft car is instant respones and doesn't forgive ratty throttle action.
I hope this helps you out mate, good luck