Not on a 35.5...
But I just got finished putting a brand new S1 in a 33. Haven't had it out on the water to finish calibration or test it yet, probably a couple of weekends wait on that yet. If you're not in a rush, I can post back when I get a chance to evaluate it better and let you know what I think. Shouldn't be too dissimilar to a 35.5.It was about a two day job putting it in (didn't have an auto-pilot mounted before, so all sensors had to have mounts fabricated from scratch) and it was problematic in parts... mounting the rudder sensor in a reasonable place on the quadrante, particularly. YMMV, this was on an older ('77) model. Without my very skinny girlfriend, probably never would have gotten it done, as I don't think I could have fit in the transom where one would have to be to get everything screwed in properly.On the whole I was happy with the mounting instructions and quality of the equipment, and it plugged right in and went to work with my existing ST60 instrumentation.