We have Maxxis ST tires on our 10K# TT and they have performed well over the last 4 years. Will go at least another year or two before replacing.
I agree on heavier 5ers that a high-end LT tire is the way to go, but Maxxis ST tires have a good reputation as long as they are not overloaded, under-inflated, and not overly driven above 65mpg although I have been guilty of doing so without any ill effects thus far.
If you are talking about using them on your Nash 5er I wouldn't hesitate as the LR E 15" Maxxis tire will do the job nicely for your size of 5er as long as rim on your 5er is rated to handle 80psi.
No experience with Carlisle ST tire although in the past they have had their share of problems, but I've heard they have been recently redesigned (according to Discount Tire) and are more durable.
They were no Maxxis readily available locally as Discount tire tried heartily to sell me an ST tire that gave them the largest profit margin like any other tire store does, just went online to DiscountTireDirect.com and had them delivered to my front door via UPS in 3 days.
Took them over to our nearest Discount Tire store and had them balanced, installed, and warranted. I have since had our local Discount Tire order me a Maxxis tire to replace an aging spare tire and they did so reluctantly (of course they attempted to sell me yet another brand ST tire) and they had it within a day so they can get them if you press them to.