100% Mesquite Wood Charcoal

I've been experimenting with different charcoals. I've had a problem with the natural wood charcoals. My Weber charcoal chimney doesn't hold enough, seemingly, to cover my grill area. In addition, after using the chimney, my charcoal seems a bit "run down" as it doesn't last very long before the temp drops. I haven't figured out what might be the problem. Either it spends too much time in the chimney (this, by the way, usually reduces the volume of charcoal by about 1/2), or it just burns faster. I don't have this prob with regular charcoal.

Does anyone have any helpful tips?

Thank you!