using HEAD's /etc/rc.d/jail on RELENG_5_1

Hi,

I'd like get the enhancements of version 1.6 of /etc/rc.d/jail in
RELENG_5_1, but I need some help/clarification:

1.- Is there any know pitfall?
2.- What's the safest & easiest way to do it?
assuming the answer to 2.- is "patch your source and upgrade"
3.- What's the one liner to create the patch needed (how much of etc/ do
I need to get)?

tks
-- 
pica