UPDATE
The 2x3s this is built from are inexpensive at a big-box store compared to 2x4s, but I got them from a steel distribution center for free (and building this took a bunch of them). The shortcoming is the free 2x3s are "seconds" and not perfect, but cheap to replace if one splits. The up side is they're thin enough to conveniently fit chainsaw bars out the sides of the box (compared to 2x4s).
Build time was 4-1/2 hours, and I used a male fun--wait, I typed "nail gun." However the sexy neighbor did stop over to see what I was up to, and she was wearing something interesting, so that's probably where 1/2 hour or so was spent. I didn't have a plan and just went for it.
The box is super-strong though does block the rear camera view of the ground, but wow it does a great job! I put chainsaw bars in the vees the uprights create to tighten chains, works awesome and saves a bunch of time because the saws, tools and fuel are right in the box. The one foot high rails are easy to lift stuff over but keep everything contained. There are about 2.5 nail gun loads of 3.5" spikes in it (nailed on opposing angles), so "a lot of them," resulting in no box flex.
The best part is the weight box has 150# of weight in it under the approximately 50# rack, plus with the rack it now carries stuff into the woods in one trip meaning it does two jobs at once. When I move to a new location stuff comes with me because it's in the box, there's no having to make multiple trips carrying it saving time and effort--that's really, really nice.
When carrying by hand cables get heavy on a long hike so I tend not to bring them and have to go back for one or more when needed, which sucks if you bring one and find two are needed. Not any more! I also don't have to go back for a trailer to haul log offcuts (twists and knots between logs that are cut out) as the box carries enough of them to balance out what's in the grapple, so while it doesn't carry "a lot" of 18" "twisty logs" it carries more than what's offcut so there's no wasted wood and no wasted trips to the log deck with a trailer of offcuts.
The Carry Sumpin' turned out to be one of my best accessories. It took time to think through the design when building it, and that investment is paying off in having a more capable product. Highly recommended.
…however, I think having a camera / display system would sure help in situations. Looks good. 
(I think it would be helpful when using front forks, at least for me it would)
