Windshields?!? Cool. I get 28-29 on mine too, but had to remove the plastic intake on the carb to go that fast, and I'm a scrawny SOB--hmmm.
Before I took off the intake, it was 26-27 and took a lot longer getting there. I'm currently doing the pantyhose trick for an air filter, but I hear there's a uni-pod filter that fits, so I'm going to try to find that.
The Batavus is much slower than by Newport, but it's also much quieter and smoother--I kinda like it.