I have to say I'd really strongly disagree with trying to remove the old anchor points on an airdeck.
As has been suggested further up you could be in for more trouble than it's worth.
Most joints from the factory are welded in these situations, and you'll end up removing a layer of the deck surface as well, creating weak spot.
Add some new points by gluing them down, it will give you two options for the tank position depending on what you're carrying, plus the option of a spare tank for longer trips or strapping down your picnic basket or other gear.
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