When I had my M3W I investgated clamps for the roll hoops rather than drilling.
I found some good ones from the USAand some from a rally car spares web site in the uk. Sorry I cannot recall either detail - but Google can maybe help.
If I was to drill them I panned to take the hoops off - not too difficult - so as to avoid drill bit slip! And to get an accurate easier job!
Hope this helps.
