I have a 1981 33' limited running 454 @ 420HP that runs right at 70 MPH. I was wondering what the design limits are of a 1981 hull design.

Is there anyone running older 33-35 foot flat decks @ 80MPH or greater?

How do they handle it?

I don't own one however I don't think your going to run out of bottom unless you plan on going really wild. I wouldn't be hesitate to take up to 90 plus anyway. Do you have hyd. steering? Check out the Cig section also?
I would have to bet there are several running over that however probably have big power plants also. Are you planning on some upgrades? A couple of 540/650hp's would be a nice package. Sleep tight. LOL...