Supercharged without automatic transmission tuning.

I have an E67 and an 5L40E that's not a supported transmission.
What do I need to work with in the E67 to get it to shift under boost considering I can't tune the TCU?
For part throttle and anything up to atmospheric pressure the transmission works as expected, but under boost I have to get out of the throttle for it to shift or else it will bounce off the rev limiter.

Also if I drop the rev limiter in the ECU will it lower the shift points for WOT shifts? I know that sounds like a dumb question, but reading about the 5L40E lead me to believe that it could be possible with certain configurations.