Rear mud guards

[metalux]

Was looking at building a tray for my single cab Hilux, and looked at prices for Hughes Sidestep Bodies and they are way overpriced. Thinking it would be cheaper just to get a box trailer with high sides and attach some wide mud guards. Just want to know if anyone has seen any mud guards similar to ones Hughes use http://www.hughesstepsidebodys.com.au/. Also does anyone know once the tub has been finished and bolted onto the ute, do you have to go for a compliance to ok everything?