I don't understand why you couldn't just insert the magazine then make a large plug in place of the release button then plug weld it in place. The mag will not be able to drop free unless you drill out the plug, that would be the same as pin and welding a muzzle device on the barrel. It would be just as difficult to remove an aluminum welded mag.
HPD makes up there own rules, knowing most people don't have the time, funds, or patience to challenge their illegal rulings.
Sir I bow to you!
"makes up there( their) own rules, knowing most people don't have the time, funds, or patience to challenge their illegal rulings."
You have just succinctly stated the entire operating position of the entire Governments of all of Hawaii and all Americans!
You have figured out what a large percentage of the population has not!
I salute you!