One MAIN thing to think about here with a lowered weedie and a using a flex/stuffing tube .
To get the height required for the prop , and considering the CG also needed for that motor , we are talking about some mighty strong angles ( bends in the stuffing tuve ) here ? .
For example - take a 36 inch boat . And say the CG is dead center . then consider the distance to the rear - 18 inches . Now , subtract at least six inches from that . ( why ? for the flex to have at least a straight run from the motor and to the prop of at least an inch and a half . and then the prop mount will have to be on the hull which also means that there is less/more room needed which will be about the additional 3 to 4 inches . ) Now take into consideration that you will need to RAISE up at least 9 to 10 inches in height , which of course , will require two bends , at that short distance , and that height , we are talking about some mighty strong angles here . And anybody that runs water propelled boats using flex cables , knows that the stuffing tube needs as little of a bend as possible , otherwise , not only do you decrease the output power of the motor to the final drive ( prop ) , but you also create a LOT of stress on both the flex and stuffing tube and or liner , which is a GREAT start for binding and snapping of the flex .
The solid shaft with u joints or cvd , would be a much better idea , I think .
Simply take a flex that you might have laying around and just try it and see what I mean ( of course , without the stuffing tube and what-nots , just compare and bend the flex to the required/needed bends.
This is just IMO .