That would seem like a prudent idea! I mean, if you want to become a test pilot then it's usual to learn to fly first isn't it? I don't have re-breather training but it seems to me that if I wanted to evaluate a new design then at the very least I would need solid practical experience of existing technology to use as a bench mark for comparison. I would also need to be very careful working with high percentages of O2 - you need very clean, O2 prepared gear.3dent:It doesnt matter how much open-circuit experience that you have, with a rebreather you will be starting over. I have a plan of action that will develop lots of rebreather-related experience along the way.