75g sump baffle widths

Ok guys hopefully this is in the right section, my question is I am using my old 75g as my sump for my 120 DT. It's my first time silicon ing glass in this way and was curious what other people have cut their dimensions for their baffles before. When I measured the width my best measurement I get is 17 3/8 inches width. Am I close? And using the 1/4 rule would I get my baffle cut at 17 1/8 wide?? Thanks for the help. And to piggy back another question in the thread, what is the best method to clean the glass before siliconing? It's an older tank I used for saltwater at one point so there is a lot of haze to the tank when it's dry, I have tried vinegar and some elbow grease but the haze is still there a little. Will this effect by bonding??