I tried the aluminium bulkheads out last night. I didn't "alloy" the entire car, just the front and rear upper and lower bulkheads, none of this centre malarky! I must say the difference is well worth the extra £. To give you an idea, I run on a very small indoor carpet track. I was one of the first cars out in practice (with a 19T) and straight from the off, my vtec 24 tyres were squealing. I used the exact same additive technique, with the only difference being the bulkheads. The car was now incredible, no scrubbing of corner speed, more predictable grip, and no squealing!
To give the car a real test, I bolted in a low-wind mod motor, and the car handled it very well.
This was also my first time running a front diff in the car, and on a track this size (see attached pic, track layout is now different) it is really the only choice when running anything faster than a stock!
Overall I'm very happy with the car, and am looking forward to Carpet Masters next weekend