I don't have the width of the opening, but I can tell you that the dimensions of the fairing are 35-3/4 inches long and the 6-5/16" tall. Hopefully this will help you.
I attached a review video for this basket for you to check out as well. view full answer...
The Curt Harness for Your Tribute, part # C55255, is actually considerably longer than that. I had it measured in our warehouse and it's about 37 inches total. view full answer...
Using an adapter to go from a 1-1/4 inch receiver to a 2 inch receiver will have zero impact on whether or not your 2009 Mazda Tribute can pull a boat. For a Class II hitch with a 1-1/4 inch receiver all you'd need is a ball mount that has the correct drop or rise which fits that size receiver. To point you in the right direction I have linked a help article for you on how to determine what drop or rise you need.
The 1-1/4 inch hitch on your '09 Tribute will not have more than a 3,500... view full answer...
I spoke with my contact at Performance Tool and she informed me that the Performance Tool Wheel Step, part # PT68ZR, has a weight limit of 300 lbs. view full answer...