Adding a folding prop will give you .3 to .6 more knots over the course which definitely helps. I installed a Martec folding prop on my Ben 331 but it was no easy proposition. When the boat was hauled out and the new prop was fitted, we realized that in the folded position, the prop would hit the rudder. We had to drop the rudder out of the boat and remove the prop shaft to shorten in a bit. Once the propshaft was shortened and the end remachined, the new prop was installed. We've lost about .5 knot in motoring speed but, it is a sailboat after all. With the Martec, there is hardly any prop walk, making it easy to back out of my slip to starboard. While the boat was hauled out, we had the bottom faired and a racing bottom sprayed on. PHRF ratings assume that you will install a folding prop, and you shouldn't be dinged. We saw a dramatic improvement in perfomance and have won a number of races and series with the new configuration.