Chalenge rating and Class

[Dark Psion]

I usually ignore chalenge level, but since I am working up an entry for the fantasy netbooks "Create a creature" contest I need some advice.

The entry for Mind flayers says they manifest their racial powers as if 8th level. If I made them actual 8th level Psions in addition to their racial powers, how would that affect challenge level?

It is currently CL:9

 

[Grazzt]

Each player character class level adds +1 to their effective CR.

 

[Krishnath]

In other words, if you added 8 levels of psion to a Mind Flayer, you would get a creature with a CR of 16