Here's the rods from a piece of concrete Reo, it looks a mess, it is a mess but it stopped the guard from flexing..

Back to the twink arch, once it's removed it's time to make the slops, polyester resin +hardener with talc added to thicken it up to an icing sugar texture, not too wet and not dry

Grab a auto body applicator and flood the arch

Now there is a time window here to get everything done, it's about 5min before the resin starts to harden so it's get the screws and drill at hand then apply the arch and screw it to the guard but not tight as this causes low spots

Once it's all screwed down, check the edge and add more resin to fill any gaps and clean up the underside as good as possible

Wait a day for it to set hard enough to remove the screws then sand and filler as needed to blend in