ive drilled wheels in the past and had no troubles, and will do if i have to in the future, there is absolutely no problem in doin this and yet again people have jumped on the bandwagon of saying its dangerous. its not, the cup of the recess still aligns the bolt, there is no difference made to the weight spread as hes using the right size bolts, it wont affect the pcd as thats set by the adaptor, the centering is done by the hub/spigot ring.
however i would have used a bench drill