Everybody covered the sizing well so all I will add is if you are looking for a mounting plate that addresses all the problems with mounting a Xi5, please take a look at the LiftSaver at www.liftsavertmmount.com
to see if it will help your installation.
It provides a more stable mounting platform, allows you to position the tm for your best fit, covers all existing holes and you don't need to drill new holes in your boat and it protects your Xi5 during launching and docking of your boat.
If you have any questions, please feel free to PM me on here or my contact info is on the website. Thank you for looking.