Stamp Options

The printing on my broken channel balance is 24 5 HR CALDWELL.
After going through the look and measurements, I'm pretty sure I need 25" 390 series. However, it's the weight option, my sash is around 29 lbs, printing above looks like I'll need 2450, but that supports up to 27 lbs.
Do I need to replace my channel balance with 2460? Will that make my sash too easy to open and always open all the way up and hard to close?
Or 2450 is just fine? Which makes it a little heavy to open, and allow the frictions for the sash to balance and stay in-place for what ever level it is opened? Hoping that the channel balance is strong enough to hold the weight.
Thank you.