Here is my design for the TikiTreiler comp. The only parts that need welding are the hub flanges on the ends of the axles. The two main parts that need to be fabricated are the spring/shock mount for the chassis rails (which are all indentical) and the spring/shock mount for the axle. Both of these are able to be cut from sheet and bent. The axle end of the shock is mounted below the axle to allow for a more effective use of the shock.
IGES File is included in zip file