Upgrade Question

Hi,

I need to upgrade two of my systems from 1.4.21.2 to 1.4.27 to address a specific bug in chan_iax. These two systems have Sangoma T1 cards in them and work flawlessly under zaptel/wanrouter drivers.

My question is, when I upgrade asterisk do I necessarily need to upgrade zaptel/libpri as well? I know the common approach is to do them all at once, but going from zaptel to dhadi I can foresee a host of things breaking (those upgrades never go well). As these are production servers I would like to avoid any problems.

Any feed back would be much apreciated.