As Ingress Field Guide(along with many other Ingress game guides) states that each portal shield placed after the first one will have diminished effect.
A type of MOD that can be installed on a Portal to increase its defense against attacks. You can deploy up to 4 shields per portal, but each shield has diminished effect after the first one.
What I wonder is, ordering of the shields after the first one is differed or not. I mean, Placing
VR, R, C, C *
VR, C, C, R *
are differed in effect?
* VR: Very Rare, R: Rare, C: Common