I am in a position similar to yours, except I have a 14" deep-V. When I bought my boat, it came with a MK Endura 40 with a 40'shaft. When the water gets rough the prop comes out of the water which creates a real pain in I disagree. So I decided to go with the MK PD 55 w/universal sonar and a 54" shaft. I spoke in person with a saleman at Cabela's and we talked this issue real hard. My biggest thing was I didnt want to have too much shaft not being able to go in the shallows, and too little that it comes out. The 55 comes with in two models, one with a 48" shaft and 54", the 54 is only $10 more for 6 more inches. The only thing is that if you are fishing shallows and you only need a little bit of shaft, you are gonna have more hanging at the top of the boat. The only problem that this creates is that it looks kind of silly, but other than that you are gonna have alot more shaft in choppy water but yo will also get to laugh at the guy who doesnt have enough. Happy trail, sorry it was so long, hope it helps.