I too have twin 40's and recently purchased permatrims. I haven't installed them yet but I have no concern about them hitting each other, etc. The installation seems clear and easy; all fasteners are provided, they are sized to your motor, and all you need to buy is a small size tube of 5200. My thinking is as follows: As compared to our old 22 cruiser, the new boat is definitely stern-heavy. (curiously, though, it absolutely pounds less in a 1 foot chop condition despite not being able to nose down as much as I like). This is due of course to the additional weight of 4-stroke motors, more batteries, large fuel tanks, etc. But the boat was designed for less weight, and I must admit the old cruiser had a lighter feel underway and a more level planing attitude. I'm thinking that the 2 Permatrims will give the boat a few inches of hydrodynamic lift in the stern, which will allow the boat to perform more like it was originally designed to, will lower my minimum planing speed, and decrease overall friction (ie water displacement) in my normal cruising speed range, which is 20mph or less. I'm also hoping the Permatrims augment the trim effect I get from twin motors, reducing the need for trim tabs, which I've declined to have installed in the interest of mechanical simplicity and hull integrity. They may well add drag at the top end. Maybe I'm just talking myself into all of these benefits, but the feedback I've gotten from here and elsewhere has been overwhelmingly positive. I will report back honestly once they're installed and I've tried them out. Best, Mike.