Guys, the current layout of surfaces on the GS tournaments is
not bad, as
@Sport says. Tennis have two majors on the
natural surface (clay (RG), grass (Wimbledon)) and two on the
artificial surface (hard (AO, USO)). HC is today the most widespread surface, so it's understandable, that HC has two GS tournaments. However, it would be worth considering whether either AO or USO would go to the carpet, then there would be four different surfaces on the GS, and a balance would be maintained - two majors at natural surface x two majors at artifical surface.