We use 1/4" Excel Racing on the I20 and I've got a tapered Samson "Ultra-Tech" halyard on my F18 (3/16" ... but it's a little small) in diameter. Both are great lines. Note that the 3/16" Excel Racing is about the same size as the 1/4" Samson UltraTech...if going Ultratech, I would recommend 1/4"...if going Excel Racing, you can step down to the 3/16".