Maybe this is rhetoric, but how do you gauge your speed? How do you know you are on the best tack and are trimmed ideally. Are there indications that other than trim just shy of leading edge luff? If you are sailing alone how do you know you are sailing the fastest that you possibly can? I watched the Lois Vuiton cup and I noticed those guys had some type of digital speed read out mounted on their mast. I suspect it was GPS linked or something of that nature. Since I am not about to put one on my boat I am wondering how everyone else does it.