Although Cabrios and Sportsters are not the same, the chassis dimension are, implying that the engine/gearbox locations are the same, and one assumes so are the seats, so the position of the gearsticks will be the same for both.
Simon Gregory built his Cabrio with the gearstick in the "normal" Marlin position, but then decided to extend his rearwards for ease of use:
Similarly I know Chris Cunliffe built his Cabrio, and then fitted a swan neck to the top of his gearstick to bring it further rearwards.
Mine is as far rearward as I could locate it without fouling on the hand brake when selecting 2nd and 4th gear.
To answer your question I think it is something you should do, rather than just consider doing.