Installed a CDI furler and new sails last year on my 27'. 135 Genoa measures Luff 33.9, leach 31.6, foot 16.6 and puts the sail just over the top of the life lines. This replaced a nearly new hank on Genoa 120 with Luff 31' - good sail and could see when tacking up wind but not a furling sail. Need to add a Genoa window for the new sail when pointing, 15 - 25 degrees of heel. Sail maker wants me to mark the location of the window. Recommendations on size, shape and location appreciated. Thanks, Bob