Here is the basis for what I built
https://forum.ih8mud.com/showthread.php?t=59928&highlight=J-moose+roof+rack
http://www.wildyoats.com/the_j-rack.htm
I did a few things different. Off the top of my head:
Outside AL wrap: This write-up uses 2"x 1/8 to wrap the sides to match the height of the ATV ramp. I used 3" so I have a 1" "lip" to keep stuff from sliding off the rack since I do not have side rails. If I want to throw a canoe on top, I will lay some 2 x 4's on the rack to give me a "spacer" over the lip.
Rear deck: Based on the photos, it looks like the rear is extended a few inches in largely a cosmetic manner simply to accommodate the radius for the rear side wrap. I used the inside of a duct tape roll for my radiuses, and I just traced it on the back corners of the ATV rack, and cut/ground a radius on the corners of the ATV rack. And attached the side wrap AL directly to the back & side of the ATV rack. I was able to use some ratchet straps to "suck" the side wrap tight around the back & side of the ATV ramp. (I had previously bent the side wrap AL strips around the end of a 48" wide piece of ply wood.)
Front "light bar": I bought 1/8 AL "L" angle and bent a front hoop rather than the rivet approach. this hoop passes under the ATV ramp for the first two rungs of the ATV ramp and is attached in multiple points. This front hoop and the side AL wraps are bolted (rather than riveted) to the roof rack. Originally I considered the front hoop more-or-less a "crumple zone" that could be replaced relatively cheaply the first time the kids drive into a parking garage !!
Hinges: I put the two ATV ramps side-by-side with the hinges on the outside. I left the hinges on the ATV ramp to use as tie down points. This means you have to put a notch in the side wrap AL but in retro-spec I am not sure they will really be that functional.
Welding The "beauty" of the J-Moose rack is that it can be built by the average stiff, with basic tools. However I have a friend that can weld AL. So I "notched" come 1/4 AL "L" angle for each of the cross bars. The sides of the ATV rails fit into the notches and are welded. This adds some strength as well as keeps the bolted ATV ramps from splaying at the bottom under weight.
Front air dam: In retro-spec I am not sure this was worth the Money. I used a piece of card board and had a local fab shop bend me a front wing out of 1/8 AL that wraps around the side a few inches. To the good: it allows me to "hide" a couple of legs that come down to the roof in the event somebody inadvertently puts some weight on the front hoop/light bar, it virtually eliminates wind noise, from the side it visually provides a little "balance" since the rain gutter mounts stop so far back from the front of the roof rack, the hidden legs provide support when I run wires from the corner of the roof rack to the corner of the ARB bumper to guide brush up and over the rack. To the bad, the bent AL for the wing cost me $120 !!!!!!
I have been on the LCML for years but just started "hanging out" on MUD about a year ago when I bought my 80. I have been largely a consumer and as a result I have not really figured out how to post pic's. But if you are interested I can try & post 'em. (as you can tell from this post I have tried to compensate for a lack of pic by typing a thousand words)