I think you should fire off a mail to FedEx post hast StudentATP, as they operate 200+ Caravan's in the US. I'm sure they'd be delighted to know they carry "too little payload" and are "not very efficient". Alternatively, you could engage brain before committing your thoughts to print.
You should also consider discontinuing using the term "planes" when referring to aircraft or, if you so please, aeroplanes.