I will likely postpone this until the winter. I was referring to drilling the screw themselves with extractor bits.
I still do not know if there is an embedded plate in the molded step, but if there is, tapping it does not sounds obvious to me. I would have to drill enough to get some clearance for the tap under the plate... but this become a bit fictional at this point until I know more about what's behind this mast step :-)
The geometry -I would just extend the slots line.. but I know, on my mast, I will not need it.
