Structural Calculations for lintels in Nudura ICF concrete

I have been contacted by a customer doing a self build to retrofit some lintels to these openings, as they have gone in without the relevant rebar installed as per the Nudura specification. Each opening only has two 12mm rebar inserted.

The build is Nudura ICF. The polystyrene on the each side is 65mm with a 150mm concrete core, and there is a 50mm timber header that could also be removed from each opening.

Having had a look at it myself, I do not know if it is feasible to place a PFC either side of the opening and bolt through to stabilise, or if the concrete will need to be cut out and a new lintel installed?

As you can see, there are 5 openings in total.