I only planted my corms a bit more than 1ft deep, but I don't see anything wrong with putting them 2ft deep as long as you don't fill the hole back up with clay soil to cut off any air flow. I think each time they produce pups, they'll get a little bit less deep, and gravitate towards their normal depth so therefore planting them deeper sounds good for colder climates.
It worked well with my 1st attempt to over-winter musa basjoo. Here's a picture of it which is a couple days old. Now it has turned green and rose a few more inches again. So counting the psued-stem underground, 2ft of it survived.
