I'm going to the lake today to measure propshaft height from the keel of my 271 fastech. Throttle up ran my slip #'s and said my slip was a little high. What is considered to be an optimal range for propshaft height? Does the stephull design play a factor?

Yes the hull design plays a huge roll in propeller depth. Stepped hulls can run at a flatter attitude therefore requiring less prop depth.

The correct depth for your hull requires considering various factors. Sinking the prop deep enough to create respectable slip numbers is the objective. However, slip numbers higher than 14-15% can be OK in certain situations if the speed and handling are in place.

Adjusting the current propeller or changing propellers can sometimes correct the high slip numbers.

You can always give Thunderbird a call to discuss their normal prop shaft depths.