In the mark2 the mast slot varies depending on the mold used. I made mine of some left over hardwood baseboard from a home improvement project. First make sure the mast is exactly in the middle then sand the blocks until they fit nicely, just touching the mast. Then glue them in place. Only the chokes in front of the mast need to be removable. The sideway chocks are always the same. Make the sideway chokes as high as the hight of the vertical part of the fore deck to spread the load as much as possible. A too small block may damage the mast due to point loading.
Don’t bother to paint or varnish, stepping the mast and sailing will rub the paint off pretty soon. Just replace when worn out. For glue I used sikaflex.