The Arneson's stick out much further than the Weismann or the Merc drives. Even with a swim plateform the props will be not be covered. If you were to jump (or fall) off the back of the boat you would be in a word of hurt with the Arneson's. If we did not use our boat at Havasu where people are jumping in the water from it the Arneson's would definitely be a consideration from a performance point of view.
I checked out the measurements of the drives on the web.
The Arneson does appear to stick out but the drives are the same leangh from the transom, 48" as the SSM#6.
How long is the Weismann?
If you are jumping to clean an outdrive, you are jumping to clear a propeller.
On the #6 there is a cover, but the Weismann and the #5 there is a propeller just like the Arneson.