Hee hee hee ha ha ho ho!!!
Sorry -- gotta laugh, cause I had/have the same prob too, with the one piece steel/rubber gasket. The canton is notorious for this (great pan otherwise though). If you look at the corners where the "half-moons" start, you'll see they're very rounded on the pan, vs the sharp corners on the engine block. To be honest, the design was poor. The answer is simple -- gobs and gobs of silicone in the corners. You should not have any leaks on the flat sides though.
BTW, any other gasket will not solve the problem, and the one-piece gasket is an excellent unit.
Hope it helps.