I have also done the rolling power brake to build boost. I can build around 18 - 20 pounds of boost from a roll, any more boost than that and the tires will start to spin badly. I have done it just for ****s and giggles on a couple of occasions. Once I tried to get a Viper GTS to race me so I did a 55 - 65 mph rolling burnout in front of him for a couple of seconds. He wouldn't bite. I must have scared the daylights out of him.
Sounds like you guys have some really nice cars.
Bob
White 93 6spd Supra, targa top, no wing, GReddy T78 turbo, GReddy 4 row intercooler, GReddy/BLITZ shorty D.P. combo, DEI thermal turbine wrap, DEI thermal header / D.P. wrap, GReddy Type R wastegate, GReddy Type R BOV, HKS fuel rail, 720cc injectors, Aeromotive FPR, dual in-tank pumps, APEXi N1, GReddy BCC, GReddy Profec B, HKS VPC, APEXi S-AFC, Greddy 52mm boost gauge, GReddy 52mm EGT gauge, Unorthodox cam gears / underdrive pulleys, GReddy turbo timer, B&M shifter, TRD pressureplate, Arizona clutch, TRD strut bar, 255/45 front and 315/35R17 Nitto drag radials out back, Redline Water Wetter, Brembo cross drilled rotors, and Brembo pads