In our experience you want to allow no room for growth, it should be a nice snug fit when they aren’t aroused at all. I guess you could get a long one that they’d grow fully into, but they don’t tend to be designed that way, most go down, and penises try to go up!
But what’s worst is having a BIT of a room to grow, so they start to get hard and then hit the end, that seems to be the worst.
Plus I like a nice snug fit because I imagine it’s my hand holding him tight. So yes, definitely go for no growth at all.