As a former owner of an '88 RAF Speed, I remember you could rig the sail so that the foot was practically on the board because it had a very deep tack strap of sorts. This was good and bad as you can imagine. It was really a very good speed sail for it's day - kilos lighter than the Gaastra Speedfoil Pro (the only real competition) and far more user friendly. You could be rigged in the time it took to put the mast up a Speedfoil. The power was very low and it even had some leech twist. The downsides were pretty in-your-face. Gybing was tough because of that foot. It did touch the water and front foot straps, and it had no bottom end power.
But as to how it would perform on today's board/fin combo is not even relevant. If Slowie sailed it with modern boards, masts, booms and fins, I've got no doubt he would go faster than Mal Wright ever did on his purple RAF's. I wasn't thinking of performance just about the funny side of sail aesthetics.

I agree with elmo too, if it's quick, not so interested in how it looks.