The Pelican tank tacks do no hold up on a boat - the plastic coating cracks and then the steel wire starts to rust. It's just my opinion, but DO NOT BUY THE PELICAN RACK!!!
The suction cup racks are very nice. Under any conditions that you will sanely encounter, they WILL hold. But geez....the price is outrageous. Even the wholesale components were too much.
I went with a bunch of the Roll Control aluminum 48" tracks with the PVC molded locking brackets without the strap. I ran some of them on a router so my fat 8" tanks would nestle a little better. I made a bunch of bungee loops to keep them all locked into place during hard offshore runs. I only installed 14 tank holders - I could always stow another slew in the otherwise totally worthless head/cabin on my center console.
Without the tanks, the racks are all but invisible under the cockpit bolsters. When I can keep my boat at the house, then I'll fabricate a tank gearing station over the livebait well on the transom. It'll make a nice backrest without the tanks too.
What you mount for boat may be totally different. I could have used dense foam cradles and kept all the tanks in the fish boxes. My wife liked that idea, except it's murder on a moving boat to keep hauling stuff out.