Here is a sample of a DIY top rack that is easy to build and very strong. It was designed by Dave Helland. I used a modified design based on his instructions. Only took a couple of evenings to make it up.
Top Rack Drawings.
Loaded rack on my Manx
2000 BAJA Trip
One of the support tubs was extended towards the front to provide a mount for the 2-way radio.
On this BAJA trip we had 3 ea. 5 gallons of fuel, 1 each 5 gallon of water, a coleman camp stove,
2 sleeping bags, food and beverages for 5 days, 5# of charcoal, clothing for 5 days- we ended
up not using 3 days of clothing. We also had tools, a bottle jack, a piece of plywood to use as a
pad for the jack, camera, tripod for camera, 2 aluminum mess kits, a spare wheel w/tire plus
a ton of stuff I can't remember.
I bet that we had 300# on the rack and had no problems. We also used old worn out coolers to
pack things that we wanted to protect from the elements, and wrapped the whole rack in a
green tarp that was also used as a ground cloth and wind protection. The rack went on and off
the buggy in 10 minutes.
10 years later I think that I would cut the load in half and have more fun. Use you imagination
and find ways to have multiple use for every thing you put on the rack,