Timing curve for my big-cam 451?

I have done plenty of experimenting on the idle already. The idle speed has to be 1100-1200 rpm since the cam has so much overlap, and a 950 cfm carb - because the vacuum signal is low. Whenever the rpm drops below that, it slowly "spirals in" with lower vac, lower rpm, lower vac... until it dies. 1200 is stable so that is where it needs to be. Adding timing (and tweaking the mixture screws) makes a little more vacuum and less chop, but 8.5" is about it.

So that takes us back to the advance curve. It doesn't ping even at the currently measured 28 deg centrifugal, off-idle. The question is, how fast should it climb to 36 deg? 2500, 3000, or what?