I didn't have to modify the brackets at all, or the Prinsu rack. Just used about 1"long 1/4" carriage bolts with nylock nuts and washers. Bolted right up. I am using the last 2 bars on the rack. Had to slide the 2nd to last bar around a bit to line up with the maxtrax mounting holes but that's about it. Maybe 10 minute install.Any shots of how you modified the brackets to get them to work with your Prinsu? Like your set up! Usually traveling with surfboards so room up top is a premium.