Well, I got the mesh onto the Sera.
No sealant involved.
One strip of aluminium from B&Q. Large sheet of mesh from B&Q - identical to the Ripspeed etc. aluminium mesh, but twice as much for less money.
Cut aluminium into small sections, fold, drill. Use JBweld like stuff (coldsteel? Putty, weird stuff) to bond brackets to bumper. Poprivet mesh onto brackets.
I can lift the whole bumper by one bracket, so I doubt the mesh will fall off, and when it comes to painting the bumper, I can drill out the rivets and put new mesh in, keeping the clean finish :)
Richard