Although I wouldn't call my search exhaustive the only reason I've found for the 100 mph vne on the models 1-3 is that the tail surfaces might flutter. I realize with the undercambered wing it will only go so fast, but I've spoken with a gentleman who has a model 1 with a rotax 670 and he informed me that he can exceed 100mph in level flight.

I'm currently doing a ground up rebuild adding more hp and doing a significant amount of aerodynamic cleanup. So given the fact that I also expect the be able to get to Vne in level flight I'm interested in knowing if there's ways to bump up Vne for the simple reason that I can see where I could easily get myself into trouble. I'm not looking to go racing. I would have chosen another plane if that were the case, this is safety I'm talking about. I don't plan to ever INTENTIONALLY exceed Vne but since I expect the aircraft to be faster its now a concern and if I can add a little more margin so much the better.

So are there additional factors besides tail flutter? Obviously balancing control surfaces would seem like somewhat of a solution but as far as I know none of the totally stock factory kits have mass balanced tail feathers, so is there some other reason the tail is prone to flutter? I am planning on making the vertical stab a lot stiffer.