This may sound pretty basic......but I'm wondering how you determine axle rating (5K vs 6K) on a trailer? If looking at a manufacturer's website and they don't list that for a particular fifth-wheel...
Our CF335SS has axles rated at 5200 lbs each. 16 inch aluminum wheels (16X6J) with 6 bolts. Weight leaving the factory was 10,014 lbs "dry". Last CAT scale Trailer Axle weight was - 9220 lbs
As soon I took delivery and got it home I checked all of the suspension bolts (many were not tightened to the correct torque spec) and found a data sheet taped to the axles - had the serial number, date/time of manufacture, weight rating and a parts listing.