My backpack fits nicely under the seat according to FAA and airline standards. My roller bag is to FAA and airline dimensions.
The width and height of the dive caddy is not the issue, its the length. Its to long to fit in the overhead depth wise, so it needs to fit sideways.
Sorry to hear so many stories of damaged, stolen, and permanently lost bags. Guess myself and family are just lucky? I will knock on wood just in case. But like I said in the past, everything in my bag is documented and insured with its own rider. If the air monkeys destroy, break, or loose it, I get new stuff. Yeah, I will be pissed for that trip, but I get new stuff.
Use TSA approved locks and they wont get cut off. Locks only keep honest people honest and scream "hey I have valuables in this bag".
I hear what you are saying, but:
1- multiple people on here who own the bag said that they have fit it in the overhead depth-wise.
2- You are talking about the size of your bags, I am talking about the number of bags
3- they were TSA locks that I was using, and they were locks that I have used for 2 years. (it was not the TSA that removed them)
You must be pretty lucky to not have any kind of baggage problem at all when you travel, or you don't travel very often. Either way I wish I had your luck