That set came out great. For $80 no harm in keeping that joker. My only thought on the shell thickness would be either:
A.) they just used whatever shells they had at the factory at the time.
B.) when using a shell without re-rings they may have decided a 12" or 13" possessed enough internal tension to be strong enough with a thinner shell and once the shells progressed to 16" they required the additional strength garnered through more plies.
How many plies is the kick drum? That might tell us something.
