Reverse gravity and concentration checks?

[ShadowfireOmega]

I have a plan for a Glabrezu to use reverse gravity on my players during round 1 of combat (straight into a spiked ceiling) and I was wondering what the concentration DC would be for the psion who most likely will be attempting to summon in his construct at that time. Would it be 20 for extremely violent movement, or 10+damage from the "fall" or 20+damage for extremely violent movement and the landing?

[Uncle Pine]

I always assumed you have to pass Concentration checks for each distraction in play, so for example a Wizard who was shot on a moving wagon would roll twice to cast (one at DC 10 and one at DC 10 + damage received).
In your case, if you rule Reverse Gravity to count as extraordinarily violent motion, the DCs would be 20 and 10 + damage from the fall.

EDIT: I just looked at the Expanded Psionics Handbook and while the SRD states that spellcasters are required to roll Concentration to cast if subjected to vigorous motions, there's no such mention in the Concentration table that refers to manifesting powers. So your Psion would only need to roll Concentration with a DC of 10 + damage from the fall.

[ShadowfireOmega]

I play with magic/psionic transparency, so anything that would affect a spell being cast will affect powers, but thanks :D