What roof top air conditioner are you using?
What roof top air conditioner are you using? Are you happy with it? Is it reliable? How noisy is it? How long have you had it? ETC....
I've read multiple accounts of people running air conditioners in non insulated van's. I don't think it makes any difference whether or not you heating or cooling, the benefit of insulating is to reduce the flow of BTU's between the outside and inside of the van--and for sound dampening.
If a 13,000 BTU cooler were quieter than an 11,000 BTU cooler I would want to go with the larger one and just run it on low. Someone posted a Promaster heat loss calculator spreadsheet but I couldn't find the link.
Reliability is a big one. I've heard bad reports on the low profile units but that could just be that people that have bad experiences make more noise. People that are happy don't say anything.