Brake residual pressure valves??????

[NTEL]

Since installing fairly large 4 pot brake calipers to the front of my TVR tasmin racer, the pedal is now long and "spongy". I've put up with this for a while and just can't get on with it. Before I go down the route of installing a large master cylinder and servo unit I was thinking about fitting residual pressure valves. Has anybody else used these to overcome a similar problem?

[NTEL]

Thanks for the replys, I thought as much. I was trying to save a bit of time and money. I have got my hands on a servo unit and a l and 1/16" MC off a subaru Impreza. Doing the calcs it would appear that this should be spot on. I'll fit them at weekend.