Actually manual J has a saftey factor built in to avoid the disappointment of being able to met customers expectations. An extra .5 ton will not handle more than 6 extra people. 20-30 is an over statement on your part. My comments about full featured a/cs referred to our fellow posters in general not you specifically.
I am trying to suppport the a/c contractors role to supply ventilation/dehumidification for the resideintal customers. That makes our dehumidifiers expensive compared to home depot. Would you be more supportive if our equipment would be available at home depot for half the price? So far there an increasing number of upscale a/c contractors promoting supplemental dehumidification. Being able to maintain the desired %RH regardless of the indoor temperature or cooling load is ideal. The ideal cooling system is a simple a/c with a whole house dehumidifier. These dehus are easy to service. I appreciate the honest feedback and understand the occasional dig. Regards TB