In my series 7 I like it around 80mph, above that it gets windy and noisy and I worry about the doors out there. I've been up to 110mph and it was fine but I mostly use it for a nice warm evening just flying around the local area and 70-80 is fine for that!

Agree with others, don't slip with both open or there will be a lot of wind coming through. Also I had my jacket fly from the back of the baggage area, over my head and out the door while on the takeoff role faster that I knew what was happening. Found it sitting on the numbers at the end of the runway on the next t&g!