I am a 48 foot guy myself. Leave the 53 foot stuff to the company drivers. I have been pulling 48 flat for 12 years and haven't regretted going this route. There may be a niche for 53 flat, and if it is common in your area then maybe that is what you need.
Now my overall opinion on 53 foot trailers, whether dry, refer or flat, is that they are overall non-sense. Ninety-five percent of freight fits on 48 foot trailers, and the only things I have seen that fill up vans and refers from front to back is toilet paper and foam insulation. If shippers needed more capacity to haul lighdter stuff, then they could use double 28 pups and gained three additional feet. Overall, the trucking industry screwed itself with 53 foot trailers for general commodities.