Hi burly,
I see that my guess about where you were in the Central Valley wasn’t the best 
Some of the better options and possibilities in the Fresno area are listed in post #2 here.
With higher weights the quality of the materials in the upper layers of the mattress become much more important because lower quality/density materials will soften and break down much more quickly. Higher weights will also tend to do better with firmer comfort and support layers as well. If you have a big difference in your weight or your individual needs and preferences then the first part of post #2 here may also be helpful.
If you follow the steps in the first post I linked one by one … and avoid major manufacturers, chain stores, or any mattress where you can’t find out the specifics of what it in it … and deal with more knowledgeable retailers or manufacturers … your odds of success will be very high :).
Phoenix