I put a 6 foot one on my 205 this summer and while we only used it twice, I was happy. 3 or 4 foot seems small, although closed bow could use less for sure. I got my from barts, with the pylon hole.
I mounted below windshield frame to the glass and am happy with that from a shade and convenience standpoint. It goes from just behind pylon to fwd on the windshield base.