We had the windshield made with a larger gap between it and the s/s surround, to make surround easier to use as a hand hold. This has worked very well. Not sure that I would want to be sat behind screen, as opposed to standing up, in the type of seas that might lead to a stuffing!
Agree that 30-ish kts is realistic top speed with a fully laden boat with full 40 galls of fuel with a 90hp honda, so you may want to look at something a bit bigger. That said, we did get 39kts on the gps surfing off a big wave over Christchurch ledge!
I must go down to the sea again......