How to reload ipf rules without disconnecting current connections?

Hello,

Sorry for this very obtuse question.

I change my ipf.conf a fair bit, and when reloading it with a short script:

#!/bin/sh

cp /etc/ipf.$1 /etc/ipf.conf
/etc/rc.d/ipfilter restart
/etc/rc.d/ipnat restart

Where I have different configurations (ipf.oh, ipf.stable etc) and I
modify the original and run "script stable" to put the ipf.stable
configuration in action. I also change ipnat. I found that if I don't
restart ipnat after ipf no nat will happen. (netbsd-2.0)

Thing is, this disconnects current connections (like ssh sessions etc).

What is the best way to update configuration without this side effect?

Sorry for the dumbness. I read about different rulesets but am not
sure how this applies here.

Thanks

Amadeus