[THX-502-L back boxes]

Klipsch just answered my email, they recomended me to try 70 liter boxes / 2.5 cu ft. Seems big? Any inputs?

[THX-502-L back boxes]

Hi! 

I have recently purchased 3 thx-502-l inwall speakers as my new LCR. Im currently used to my RP-280f and RP-450c, but due to space issues i have to use inwalls instead. 
These speakers have a infinitive baffle design, but if it improves sound quality or general performance of the speakers i am more than willing to build back boxes. 
I cant seem to find any specs from klipsch tho on what size (volume) to build the boxes at. Any clues? My dealer told me anything between 25-30 liters is good. But it would be nice to double-check it with people that knows klipsch products better then anybody esle, you guys I dont want to restrain these speakers either. 

Kind regards! 
Andreas