I have one of the early TI's that didn't include foam. One of the first things I did was to install NRS float bags inside the bow and stern. Both bags are clipped in so they're secure but easy to remove. I've never had a problem with interference of rudder lines, nor have I had any issues with storage at either end of the hull.
I read all the posts above and was impressed with some of the math that others have done, and many suggestions are great ideas. Nonetheless, I simply feel more secure on the water with the purpose-built flotation bags.
I was in a search and rescue helocopter squadron in the U.S. Navy, and one thing I learned is that water is absolutely unforgiving. As such, I'd never trust my life to simply cramming a pool noodle into the hull. You spent a LOT of money on the boat. A few more bucks for two flotation bags won't break the bank.
Good advice I think, and for the type of use I am doing storage is not too much of an issue. My flotation bags are in and so far no issues.