The new blocks are all narrower than the std X block.
The range goes, from widest to narrowest:
D, C, B, A, X, XA, XB, XC, XD
I know some guys on here have the blocks, I personally don't, so I can't comment on what affect they have on the performance.
Also, I tried some setup changes on the car today (rubber tyres on carpet), basically the adjusts that we could see from I tried pro-dive on the front (placed 0.7mm spacers under the A-bridge) and i also lowered the steering rack (placed all three spacers on top of the steering knuckles) and used 4mm of spacers under the ball joint.
Car worked very well, really turning in well whilst running spool, combined with the narrow rear end, the car was awesome. Easily the best handling I've had it with the spool. Results wise, qualified 2nd in the A, ended up finishing third after an unlucky moment with a backmarker in the final minute. Incidently we were running 6 minute heats with 27t motors, car certainly woked well, and didn't really notice the extra time.
Hope it helps
Ed