@jzchen thanks, yes, I already have the fit kit, I purchased it along with the feet from someone who's dad had a C-Max in the past (feet + fit kit were a grand total of $40 CAD)
I also purchased aeroblades for $200 CAD, I had to play ball with what the seller wanted because I wanted to avoid new, and it's not easy getting the specific length of 53" on used sites, so if something comes along, you grab it!
I finally picked up the vehicle yesterday (yay!) and have only attempted a perfuntory attempt to slide the feet onto the bar.. as you can see from the side shot (posted above), the interface between the foot and the bar doesn't seem to rely on the smaller slot under the bar, but instead struggles to slot into the larger channel above this slot.
Photos of the feet in some manuals show a smaller interface that I assume fits the channel, I am now wondering if:
there were either multiple versions of the 480R feet (and/or)
I can lube up the existing interface and bang it on with a rubber mallet (and/or)
I can purchase a different interface for the existing feet that fits the channel (or)
I need to purchase an updated set of feet
I will continue to test and report back as I continue this complicated journey!