correct the plates are cut around the armrest to fit but just on the bottom side. Little more detail in my build.
attachment front system: Top secure point is to the extrusion, I used my 1/4-20 threaded rod instead of their bolts, bottom is to either seat mount bolt thread. It provides (2) mounting points and a strap, they also can be ordered separate later. I thought it was a little redneck at first but it works ok. I get it if removing to add a seat.
There is a group here in Colorado that has a rear system you may consider as well, they have posted here a few times and similar to this but much cheaper. I chose this because its more closed in and I wanted it as low as possible. Theirs sits a bit higher than I care to go.
View attachment 2999405
I can get a better close up if needed:
View attachment 2999426
pre adjustment and secured
View attachment 2999428