an old prof of mine who taught ship dynamics. He is now the NAME dept head at UNO. http://www.name.uno.edu/faculty/wsvorus.aspx Even if he isn't able to look at your situation in depth, he might give you some names or a hint about the most likely route to take.

That looks like a very clean installation with plenty of clearance.

I'd be inclined towards the 3 blade, but I really don't know enough about it to gamble 3k on it.

Keep us posted on what the solution turns out to be, please!

Tod