Call Ultimate converter and see what they can do.
I was thinking of using a 9.5" converter for some street/strip driving and they set me up with a really tight 9" that will flash stall to 5,000 RPM, but acts like an 11" converter until I put my foot to the throttle. It's hard to explain, but I used to run a 10" Dynamic Race converter, and it would want to goto 2,800-3,200 RPM at lower speeds, and it would flash to about 3,500-3,800.
The ultimate seems to be so tight, that the engine RPM does not really seem to be much above what it should for the speed when at partial throttle, but when I get into the carb secondaries the converter starts to flash to around 5,000 RPM.