Send me an e-mail to remind me (rightclick@mi-connection.com) to take some pictures and describe the setup for you. It's a bit of a PITA, but can be done. I do believe it's 3/16th", but don't go out buying anything yet until I've made sure. It has to be the perfect size to fit through the gudgeons and allow clearance for the tiller crossbar bolts to go through and in between the two lines.