I wanted to do the same, but a hydraulic line is in the way. Might see what I can do to shift the placement of the rear tanks.

I think that hydraulic line is why the website lists 60lbs as max capacity.

Four tanks equals 60#, as they only put 15#per cylinder now, at least in CA—not sure if that’s a federal or state mandate.
I also had to move some lines around. Not a big deal. Used zip ties...
So now, instead o the front two tanks leading the charge to power the heater, etc, I use the rear two ones. The front ones we use for the outdoor grill or heater.