The following links provide some useful information on how to accurately trim your aircraft. While this is something we should do for all our aircraft it is even more critical if you intend performing aerobatics to a high standard – i.e. not just tugging the sticks to do the manoeuvre and accept the result!
Once well trimmed there are also some links on aerobatics
International Aerobatic Club Manoeuvres
The theory and practical of a good take off