If your having a trailer made, then go for Air Suspesion units, definately three axles with big tyres these will soak up sudden jolts and bumps, and generally be far easier on the loaded Heli, but the heli would need to be very tightly fastened down, with some overcentre clatches on the skids so the Heli effectively is at one with the trailer bed, with your blades held in more than one place ( ie not just tied from the ends as normal) a yolk and brace system would need to be fitted that would hold securely the full length of the blades, with careful dsign you would be able to go off road with such a trailer.
Let us all know what you do with piccies if poss
Peter R-B
Vfr