Ok Norm, I have just come back from bunnings
Had a look at the thunder while there (figured if I break theirs trying to get the silver cowl off there is no problem haha)
effectively at the back of the engine (catcher side of mower) there are the two clips. You can just see a 1cm wide square hole in the black cowl where the silver starts. each hole has 2 downward latches from the silver that face rearwards. if you stick a small flat screwdriver in at each edge of the holes and push the top of the screwdriver toward the catcher, you will disengage the latches
Alternatively, the plastic is so thin that you can grab where the rounded corners are and gently bend and pull upwards
