If I read that right, you want to add an over-shield to a unit?
Assuming you've started a project already, you'd put this code in the unit's default odf.
MaxShield = 400
AddShield = 5
So if you're adding it to the stock officer you'd put it here, rep_inf_default_officer.
Of course you can play with those numbers to change the shield strength and recharge rate.
MaxShield is the shields strength
AddShield is the shields recharge rate
Hopefully this helped some