As an instructor who has flown in convective regions a lot - I know how difficult it can be.
Having said that if your up and down consistently by +/- 200' I would suggest this represents a more fundamental problem with trimming or the way you hold the control column.
I would very strongly urge you to have a flight with an instructor to rectify this situation as soon as possible - as trying to rectify this during a CPL course is difficult as a certain skill level is all ready assumed - and it is also normally pretty expensive to fix at CPL rates.
Get it fixed early - otherwise your going to pay for it later (ability and financially)