There's a rule you have to bring your carry on when you check in?
Um, someone sells you a ticket and the contract of carriage says that they allow you to bring a carry-on up to 7kg for free, and if its more it needs to get checked for a charge- so you hide it at check-in and tell them that you don't have any luggage...
No there's no rule you need to travel with a carry on.
Just not to be a lying thief.
(trying to make it not so noticeable at check in is one thing, the others are just straight gneiva)
Kenny is a frume yid, and gneivas/matteh akum is asur anyway, but go ahead and rationalize it anyway you want.
And cry me a river about your tallis and tefillin taking up all the weight - that's the same cost of being a Yid as paying more for meat is. You're just rationalising sheker.
(Anyway, you could always put them on at check-in...)