My issue wouldn't be with the shelving stability but with the ability to safely take down and carry something large while hanging on. I get it, sometimes you can make things work, but there's going to be the one time where something goes wrong too, and that's probably why policy and OSHA rules are in place, because it's happened before.

That you don't have the right equipment to do things correctly is a problem waiting to happen. It's not a rare thing, companies like to trim and slide by as much as they feel they can, while quoting the "safety first" mantra. That's why you quote that right back at them when asked to do things, especially when they don't provide the means. This is also where HR can be on your side, since HR is all about protecting the company via their policy. As long as you and the policy are saying the same thing, HR is your ally. That's the only time.