Yes - have used these in several boats now - I use the folding tank holders so that they can be folded down out of the way when not in use - these works great and hold the tanks in place - make sure you adjust them to fit the tanks you have (7.25" dia or 8" dia)
The plastic tank holders are what fold down - they slide into the aluminum rail, which I mounted to the gunnel under the bolsters using aluminum stock so that there are no visible holes down the road is I ever take the aluminum tracks off the boat.
I mounted 2 rails, one under each bollister on my 33. Used stainless wing nuts and mounted to the rod holder frame. Each holds 4 tanks and the holders fold away. Works great. Remove it when you don't need it.