As a demonstration pilot on the whole range of Pierre Robin aeroplanes some few years ago now, including the HR 200, which was meant for aeros, I never wore a chute, neither did I wear one in competition aerobatics in Stampes, Tigers and a CAP10. It is very much a matter of choice. It simply is a fact that if you are at ease with yourself and your aircraft you don't need one! The Chipmunk however, IS one aircraft I might have thought twice about it, especially when spinning.
But if you think of the situations that may make you think you need one, you are perhaps doing it wrong, especially if you have frightened yourself. I very much doubt that you would get a structural failure in a Robin and + 6 is fine and just half a point lower than 'normal' in negative on most other aerobatic aircraft. Also not a problem.
Robin aircraft are the one of the safest private aircraft ever built and I have never seen anyone wear a chute in one.
Concentrate on doing the aeros right, to perfection even, and you will feel the same as we did.