Free air wire sizing and derating

[kahanek]

I am trying to determine the number of conductors required to connect two portions of bus that are approx. 3 feet apart. The conductors must carry 3608 amps. I am attempting to make this connection with 600v, 600kcmil cu. wire. The conductors will not be bundled (in my opinion), nor in conduit. They extend from each phase of a 3000kVA transformer bushing approximateing 5/8" thick to a bus comprised of 4-1/4" X 6" bus bars. All cables will be landed on hole patterns 1 3/4" on center, cables will be bolted back to back on either side of the buses. All the cable and both buses are located in the transformer cabinet which will be exposed to direct sunlight. I am planning on using table 310.17 (single insulated cond. in free air). Is that a correct? Can these conductors be classified as "in free air" as there is essentialy no circuition of air in this cabinet. Also, do I derate for the ambient temperature I expect in the cabinet? Is that all? Thanks for your help in advance.