Does your 22 rest on its keel (or similar structure) on the trailer? I would think it would. I would also think that Catalina could tell you what depth of a snow load the trailer and boat can carry.
With my C22, the Swing Keel, doesn't totally sit on the trailer when retracted.
When trailering, the lower end of the keel rests on it's bunk, simply because it's recommended to slack off the keel winch so that the some of the load of the keel is sitting on the trailer itself, once the boat has been loaded on it.
The upper end of the keel is a small distance above the trailer. Maybe an inch. That way it easily clears the trailer when launching/retrieving.
To have the keel take some of the load, the hull would have to flex enough for the upper end of the keel to touch the trailer, while the lower end of the keel was pushed upwards into the trunk.
So in this case the additional snow load is on the hull sections that rest on 2 bunks and a roller.
Unfortunately, I can't see Catalina being much help, since it's not the original trailer.
Most C22 trailers I've seen have all been different. Each one has slightly different bunk placements/widths/lengths,, which would change the loading.
That said, the boat should be ok but I'm not as sure as I'd like.
For that reason I've decided to put a tarp over the unstepped mast, covering the hatch and the cockpit.
This is mainly to protect the teak from UV damage and to only minimize snow drifting into the cockpit's "hollow".
The tarp is far from fully enclosing the cockpit, so ventilation won't be an issue.
I plan on checking on the boat occasionally to see how much the hull flexes with the snow that does accumulate and remove it if needed.
In the spring I'll remove most of the snow before it starts melting.
Unfortunately, I ran out of time to get my new powerboat cover modified in time to be able to use it on the sailboat for winter.
I believe that there are three main considerations that cause me to cover every winter. First is uv protection, especially the brightwork. Second is guarding against both deck leaks and freeze thaw cycles causing leaks under hardware. Third is to prevent broken scuppers from draining a full winters worth of snow into the engine room.
I think you concerns are valid, especially in your area of North America.
UV protection makes sense in any location. I've got a summer cover that, once fit to the boat, will protect the brightwork and deck from UV, and tree sap.
Assuming that someone has kept a handle on bedding hardware, and has potted all the deck hardware holes with epoxy, they shouldn't have leaks, and minimal risk from developing them.
With no leaks, I can't see how cold weather will do much of anything, unless the compound someone used for bedding becomes so rigid as to fail under cold temp contraction.
Of course, there is always a chance you could have an unknown minor leak that would be made worse by a freeze/thaw cycle.
In my climate, it simply gets cold in winter. We don't have many freeze thaw cycles.
Winter is here ! Winter is gone ! Fall and Spring are just ideas here.
In a more mild climate where a lot of wet snow, and variable temperatures occur, I can see how the risk would be much higher.
On later C22s the scuppers drain through the transom, so them leaking into the hull is not much of a concern unless the scuppers are leaking for some time and the transom delaminated.
IMO, covers have major location considerations.
A friend had his boat wrapped, and he stored it out on his farm beside some bush. Even with repellents, squirrels would get under the cover and make a home. On year they chewed his trailer wiring. Other times it was mice.
He no longer covers his boat, and it's no longer a cozy place to build a rodent home.
Someone with a boat stored in an urban setting likely wouldn't have the same animal problem.
Someone who lives in a humid, warm place would need to protect against rain, and moisture inside the cabin.
Someone, like me, who lives in a place where winter temps are cold, and the winter humidity so low as to require skin moisturizers, doesn't require the same level of ventilation and has more worry about having the roof sloped enough to shed the snow vs rain.
Then you have all the variances in between.
Until now, it's not something I really thought about.
Thanks for the "food for thought" !