Shadow Field question

I've been thinking of how to get the most out of my sf archon.

Can i use his 4/5+ before i use the 2++
for example my squad with archon gets shot at with small arms fire (<S6)
He takes 1-2 wounds on his regular save
I know im going into a challenge next round with him against >S6
so he'll get instagibbed with the first sf fail meaning 2 wounds are lost to id

No, you have to use best save available, always.

Crap

But if you manage to get 2+ Cover (night fight) you could use that.

Put your troops in front of him to take the wounds.