Mack I'm afraid Dan's gonna be right re that swim platform...and with the way the ladder retracts into it, notching it out might not be an option...
Here's the way I did mine on the 74...
And had to do same on the 21...
I still have the swim platform shown on the 74 in case you can use it...
Good luck w/it and let us know what happens...but whatever you gotta do to get a set of tabs on, it'll be worth it fo sho!!