Attach tape measure firmly to topping lift at a point 12" above the boom. From there measure forward to the top of the mainsail at the sail track, then forward to the tack of the mainsail at the intersection of top of boom and the back of the mast. DO NOT PULL, DEFLECT, BEND the topping lift forward when you do this or your dimension (and the cover) will end up too short. Best to super tighten the mainsheet to load up the topping lift before measuring.

Now measure from top of the boom, at the mast, to the top of furled sail, at the mast. DO NOT ADD ANYTHING---we will add to your measurement to make room at the top.

If you want a really nice installation, or don't have a topping lift, we offer a stand-up bracket that mounts t the end of the boom, The cover is tied to this instead of the topping lift. $130.

We will add a flap to the length dimension so that it will install just onto the mast by about two to three inches. we assume there is no obstruction in this area.