I think you'll be very unhappy w/a fixed prop unless you install a shaft brake. A spinning prop of course will affect your sailing performance quite a bit, but the noise is of a lot greater concern, at least to us.
As much as I hate to say it, I doubt that you will regret biting the bullet and buy the MaxProp. However, if you are venturing far a field, you should consider carrying a spare prop (a two blade is easiest to store and cheapest), key and nut, should there be a problem w/the MaxProp.
We love our MaxProp, by the way. Works very well and the boat handles very well under power. Many, many cruisers down here in the Caribbean are using them now.
"Any a**hole can make a boat go; it takes a sailor to stop one"
Spike Africa, aboard the Schooner Wanderer
, Sausalito, Ca. 1964