Default [Q] Regain storage space when downgrading CM

I have tried CM 10.2 on my I9000 for a few weeks now but want to downgrade back to 10.0.
In my opinion 10.1 and 10.2 are less smooth.

I have read in the FAQ in the CM 10.2 topic the following;
Due to larger size required for newer versions of Android and CM improvements, space has to be taken from /data for system apps.

Do I regain this space automatically after downgrading?
(Can I downgrade from 10.2 to 10.0 just by installing this version?)