To the best of my knowledge, the Transgo TF-2 (auto vb) is NOT a low-band apply modification. To get the low band to apply, you still have to manually shift the trans into low. For this reason, I would always manually shift the trans into low when starting a burnout, OR and especially when launching the car. Otherwise, you're relying on the sprag to hold 1st gear.

(at least this is how my trans builder explained it to me... )

I have the TF-2 vb. I start my burnout in 1st and quickly move to second as soon as I get the tires rotating along. Try to avoid "catching" the tires while still under power when pulling out. This procedure seems to be working for my 727.