I'm about to upgrade my '08 coastal's cage. She's over 3 1/2 feet long, should be hitting 4 foot in no time.

My question is, should I go ahead and invest in a 4 foot AP cage, or would that be too big for her?

She really is quite tiny when she's coiled up, fits in hides that are suitable for BPs around 100-300grams.. but when she explores her cage at night she definitely looks like she'd enjoy having more space.

I'm wary to change things up when a snake is pounding food, best sign of low stress.