Just to clarify your question, the rear axles are 1 piece but the flange is not integral to the shaft, it is a tapered, keyed fit, retained with nut. There is an additional exploded view in the Roxor Off-road parts book, page #U4A140005.
I think they'll be fine within reason, excessive tires, loading etc. This is old school and I'm not worried, I use mine on the farm and in 4WD, don't abuse but don't baby