It's been my persoanl experience that in order to take full advantage of a torque converter (3800 in my case), I had to take the car to the track and "Test and Tune" (like you're doing) until I thought the wheels were gonna come off. However, I don't think you're taking full advantage of the stall by power braking, rolling forward, then nailing it.
The stall is intended to allow the car to launch at an rpm where your torque curve is 'fat' (versus 'skinny'???). A lot of variables go into determining the correct convertor for you car. The car's weight, the engine's torque curve and the amount of horse power you have available to support the torque the engine makes (horsepower is what allows the engine's ability to achieve and mantain torque).
So, having confused myself enough, on to what you already have and me offernig a humble opinion on how to optimize your setup.
Use the convertors "FLASH". This will allow your engine to leave at a higher value of torque. A couple of things to study here.
1) Tire spin. Launching at a higher r.p.m. (thus higher torque) requires that you have minimized tire spin. The tires have to be wide enough and have the correct amount of pressure to solve that problem (but that's another chapter).
2) Timing the tree. Because the car is launching at "FLASH" stall now, there is a time delay from the time you floor it until the flash kicks in. Only by practicing(or going to "test and tune") will you achieve what's best for your setup.
I'd pay VERY close attention to your 60' times. That is where you're going to take advantage of the magnitude of being able to reduce your e.t.
At your T-n-T sessions, record each run's setup (ie., tire pressure, launch rpm, 60' time, etc.). Also, try to be consistant when staging, either short-stage or deep-stage to eliminate another variable. I suggest shallow stage at first (roll the car to light full stage then stop - no inching forward). You can practice on that technique once you find out what your car's optimum launch variables are. Also, don't be too concerned about your r/t. - yet.
When testing and tuning, change only one variable at a time - (I'm guilty of not sticking to this very important point). In order to determine what effect a certain change had on your e.t., you HAVE to eliminate as many variables as possible.
Once you've determined the optimum rpm launch and tire pressure, then work on timing the tree(reaction time).
In my case, I have found that leaving on the second amber, at 1500 rpm's, gave me the quickest 60's. This is only related to my car. Each vehicle is different. The car's weight, weight transfer, engine h.p. and torqe, rear gear ratio, tranny ratio's all are different and make up a car's "system".
Using a 'system' approach will help optimzie a car's performance.
A few notes on cutting a good light during your staging(once you've optimized your 60') is to:
1) Assuming you've performed the same type of burn out you've found to be best for your car, slowly roll in to light the 1st yellow and wait until the opposite lane's car has lit his pre-stage light - "courtesy staging").
2) Now turn your attention to the second amber. Yes, 'AMBER' not the second yellow. Odds are, you are going to be leaving off this light. There is where you want to concentrate 90% of your thoughts during this point of staging.
3) Raise your rpm's to whatever you've determined you should leave at. By easing up on the brake and keeping the rpms at the pre-determined amount - and STILL looking at the 2nd AMBER light, ease forward until you see the 2nd YELLOW (fully staged)light come on in your PEREPHERAL vision. Trust me, you'll see it.
4) Now, ALL your focus, 100%, is on that second AMBER light - not your opponent, not your rpm, NOTHING but that light. Again, your peripheral vision will allow you to see when that second yellow is coming on.
5) As soon as you see the second AMBER light come on, have confidence your not leaving too early, then launch the car.
6) Return to your pit and show your buddies your .5XX r/t.
There's no substitute for practice. Practice, practice, practice.
Please realize I am in no way, a professional at this. I'm simply sharing MY personal experience on the subject.
As the small print at the end of weight loss commercials read, "individual results may vary".
Good luck and keep us posted,