Trans brake launch options

I have been using the power grid with a two-step at launch (max spark advance) then using a timing curve to launch the car and minimize tire shake. I currently leave at full throttle on the two-step at 4000-rpm. I will not be able to use the two-step or a pneumatic air launch in 2015 (different racing organization). I am also concerned about my use of the two-step because I had cracks in my crankshaft that I feel were a result of the way a two-step holds the RPM while the car is on the trans brake.

My questions:

1. Has anyone ever tried to pull timing out while the car is on the trans- brake to hold the RPM then bring in the timing on a ramp instead of a curve? It would seem that this would be easier on the crankshaft because all cylinders would be firing at the same location (in relation to TDC) and not periodically removing the fire from a cylinder in the firing order to maintain Launch RPM.

2. Is there some advantage to launch at part throttle that I am overlooking? I noticed that several TD competitors are using a pneumatic air throttle (part throttle launch) control and trimming the RPM with the two-step.

My combination is 125-wheel base altered, 1950lbs, 500-CID dodge wedge, 1471HH, expected to run in the 6.60- 6.90 et range.