"I am running ellegi 40shore fronts (26mm) all round. We race on a asphalt school ground, and due to the crown on the surface for run-off of rain, most of the corners end out being a bit off camber. Other people are using 40shore tyres and seem to have success (with other chassis) so I am not 100% convinced that this is where I am losing traction (though one rear tyre was pretty tapered due to a previous bad wheel alignment with too much camber so maybe this is a contributing factor)"
You might want to try to cut down some 40 Rear tires to 26 or 28mm as well. I think actual rear tires will help you, as the rubber is a bit different. If you run a wider hex, like the 6.2mm or whatever it is, you may be able to get a 30mm tire on with the shock in the middle hole on the arm. That wider hex will get you at right about 190 with most rims. As a last resort, if you can get Eagle foam tires in your area, they are all 26mm.
ps. to all they guys running carpet/foam- The Kevin K setup kicks ass. I got away from it for a little bit, and now have come back. Try it and you'll see why.