Stacking wire crates?

Do any of you have stacked wire crates, and if so, do they work well?

I'm trying to rearrange to make more space. I have a 48" crate for Logan that has a thick plywood topper on it, and a 36" crate for Gavroche. I know the topper can hold Logan at 70ish pounds because I used it as a grooming table at the dog show. Gavroche is 53ish pounds. I don't plan on crating the dogs often, if at all, once I'm done rearranging. If I do crate, Logan is the most likely to be crated if they're both home. Otherwise it's Gavroche home by himself, and then he can go in the big crate.

Do you think stacking the two would work and be safe? Do you/should you attach the two crates together? I could easily drill more holes in the plywood if I needed to to make more attachment points.

my only input is to make sure the plywood is bigger than, and sits on top of, the lower crate, not "inside" the rim made by the sidewalls, as that will bow the top and cause damage

Yeah, the plywood is definitely bigger than the crate and fits over the edges. I have them stacked now but not secured, and it seems okay. Like I said I'm not going to have dogs in the top one regularly, and probably only with supervision. The plywood is also quite thick, 4-ply and 5/8" thick. I had a hell of a time drilling holes in it for some reason.

I'm trying to decide of I want to paint the plywood or stain/seal it.

I personally would not do it .

Wire crates are not designed to hold weight. If you have no other option, then design the top so that it overhangs and has legs. The corners are weak points as far as structural integrity goes and as wire crates are collapsible you will need the added strength to prevent an accident. Also, while your base crate likely COULD support 50 odd lbs of stationary weight with the help of load distribution from the plywood (don't forget to factor its weight as well) it really should not be expected to bear it while your animals are inside. All it takes is one time for the dog in the top crate to move just so at the same time the bottom dog moves just ooppositely so and collapse the whole shebang on the dog below. Not a chance Iwould personally be willing to take.