I got the same box on the rear of my outlander, you can fit a lot of gear in that box. No trouble to fit a chainsaw in there, along with other supplies. Im pleased with the box, Ive had it on about two years now.
It's a good box very solid and will hold anything I want to bring. The directions are crap and amazon (where my wife bought it ) states it will mount right up to a 15 Max outlander....it will not but you can make it fit. I chose not to drill any additional holes in my rack so I used the location of the existing torque head bolts. Below is ho I did it
Take the rear rack off, put the brp case upside-down aand place your rear rack on the brp case. Remove and Match the 6 torque head bolt holes and mark the bottom of the brp box. Drill the 6 holes out and go buy 6 1/4 - 20 2 inch bolts and 6 fender well washers...the washers are about 4 inch radius to spread out the stress of the 6 mounting points.