ASM
If bits cracked off I can only assume you were being a bit heavy handed / rushing !?

I use a dremel with a small drill bit to run a load of holes along the line to cut, then use the drill to connect the dots, then a sanding end to smoothen it up and Ive never had any trouble...

Not likely to be the quality of the cowl in question I would say..

We just had some great feedback in from Ireland on the C50 ! Took a Madness head on apparently and matched performance !? Interesting !