Enclosure size?

Hello all! I have a question regarding enclosure size for a 5 foot long corn snake. I may be adopting an 11 year old corn snake from a friend who cannot care for him.

I have one corn snake who is on the smaller end (only 3.5 feet and four years old) and I keep her in a 30 gallon enclosure.

Is this a suitable size for a 5 foot long corn snake? Or should I get a larger one? All the care sheets I have looked at suggest 20 gallons but that seems kind of small for a big old guy.

I appreciate any help! Thanks.

The two rules of thumb that I've read over and over again are as follows:
1. Your enclosure should have a minimum of square feet equal to the length of your snake.
2. Your enclosure should have a minimum perimeter equal to twice the length of your snake.
Assuming a 30 gallon is approximately 3' x 18" (according to google) that would make it appropriate for a 4.5' snake by both rules.

So my guess would be that it would probably be fine, but that your 5 footer would probably appreciate even more room if you can manage it.

Thank you!