A few minutes here and there, and this is where I am at with my 379 Pete project. My other time has been spent designing new models. I just recently completed an MAC 48' all aluminum flatbed. I have a pair on order now.
This model will also make a nice day cab tractor, which will require a slight design modification to the frame, and the addition of a 5th wheel.
Here is the 3d rendering on Shapeways of my MAC 48' flatbed trailer: