Trailer Tongue Locks to prevent theft.

Thanks, good to know.  Hardened steel at least makes them use a power tool (such as a grinder) to cut it, which makes noise.  Just like with bike locks, a determined thief can break or cut through anything.  Heck, in big cities, the bike thiefs use cryogenics to freeze the steel and then shatter it with a hammer.  We can't protect against everything, but if we slow them down, they hopefully move on to easier prey.

The lock you describe appears to be the one sold on Amazon as the "Trimax UMAX100".  I might give it a try.  

I will have multiple lines of defense, including a locked gate and security cameras.  But our baby will be located at our second home and we will not be there all the time.  

As far as the video showing quick removals I have 2 points to bring up.
1; The amount of noise generated to remove the locks would surely draw attention to the theft.
2; Once again I state, the locks are meant as a deterrent to theft, not a prevention. Where and how you park is also deterrent not prevention.

Main thing to face up to is a thief is lazy and will go for easier pickings. They will always take the one sitting next to yours with no lock at all on it. Again as stated before, 9 times out of ten the crack head wants what is inside the trailer not the whole trailer. Let's face it, I know how much these scrap for and it just isn't worth stealing a trailer to scrap. On average they will scrap for less than $500 if you take the time to part out first. Taking the time to part out will almost surley get you busted from advertising the parts.

I'm still in the camp of using as lock is better than not using one.

If your dumb enough to park/store your lovingly restored vintage trailer in a store and lock facility then it might be stolen. If you park it in your driveway with no lock at all on it, not being fenced in with no one watching it, you might have it stolen.

You have to take some counter measures to theft even if it is just to slow them down and have the theft cause a bunch of noise. Noise draws attention.

There is no way a trailer or anything else could be stolen from my property with a lock on it. It would cause too much noise. My neighbors would have guns drawn and the cops on the way. Heck a couple of my neighbors would shoot first and then call the cops! I've got very nosey protective neighbors who own guns LOL.

You guys need to think out of the box. An alternative to locking the tongue would be to:

Just "slam" the trailer. 

I have a tongue lock, and used to worry all the time about theft... Now, in between campouts or if not using again for more than a week, I just jack up the trailer, take the tires off and leave on blocks. No-one is towing it out of there!
I always do this in the winter too... tires will last longer.