We always had our SR4 on a tiller steering (Merc 25) and it had excellent steering conditions, even on a 5 beaufort Norhtsea. The only thing you are going to notice, is that the tiller is quite far away when steering left arm, sitting on the right tube. No problem cruising, but full throttle at sea forces the driver to sit on the floor, which is not that bad, because the centerpoint of gravity lower along with that action.
When you decide to use the tiller setup, you should try to lift up the engine about 2cm (we put a little stainles steel beam between motorplate and bracket). This will probably ingrease full throttle handling, as it did with mine. We also made a flat aluminium build-in fuel tank, which we include into the bottom for more flat floor space and a better centre point of gravity (flooding hull holes closed of course). See the link for pictures
Grz. wouter (NL)