Many seem to forget what a torque converter does. It multiplies torque. The lock up feature removes that multiplication. It's nice on the highway for sure but it can also be a pain in the backside on the drag strip.
Lock up has zero multiplication. Max multiplication occurs at the launch, and it diminishes as you reach the top of each gear, then right after you shift, you get some of it back again after the shift occurs. Also the slip you get between shifts actually helps keep the engine in it's power curve. But excessive slippage at the far end of the track can slow it down. But I think people place too much emphasis on slippage. A junk converter off the shelf will do that from time to time. Most GOOD converter builders will know what to do, and they're not cheap. You get what you pay for. Lockup is, again, nice to have on the highway. IMO if you're not driving on the streets much, I don't see a need for it. But I have not used lockup to split gears either. I could see that as a potential benefit depending on the converter. I wonder how much RPM drop there is between non-lock and lock at the top of high gear?
Sometimes going back to the KISS principle makes for a more enjoyable racing experience. And in my case, more successful.
'92GT, 427" and '93 "LXVO" coupe