I have a similarly shaped head and have also found that the Bell helmets work the best for fit. I tried a bunch of Giro's and none of them worked. I also tried Specialized and LG, and neither of them worked either. I currently have a Giant Ares that is *decent* (ie. no actual rocking but it's a little tight front-to-back because I sized down for the side issue) but it's not ideal.

I think that for my next helmet, I'll go back to Bell.