This was inspired by something in Sharkey's thread. I'll give a bit more detail here as well as an additional attachment method.
What you need:
M8-1.25x30mm cap screw (aka bolt), qty: 2 - mine are grade 5 steel, didn't have grade 8 SS in metric and probably not necessary, cost $0.25 each, length not super critical, just get something around 30mm
Climbing bolt hanger, qty: 2 - mine have a rating of 35 kN (i.e. it's not going to break) and cost $3.50/each
Lighter
Nail
Pliers, needlenose or regular
Here is a pic of the bolts and climbing bolt hangers
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First step, unzip the roll cage cover using the zipper that runs left to right across the rear cross member. When looking at it from the cargo area, you'll see two nuts that look like this, one on the left and one on the right:
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Now that you know where they are and what you're going for, zip it back up and feel for them by hand through the fabric.
Next, grasp the nail with the pliers and use the lighter to heat it up nice and hot. Only takes about 15-20 seconds to get it hot enough.
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Now push the nail through the fabric into the holes we located previously. Move it around a bit. It will melt the fabric, helping to prevent it from further tears. Repeat a few more times, widening the hole in the fabric each time until it's the size of the hole in the crossbar. When finished it looks like this:
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Next, take your M8 bolts and your bolt hangers and screw them in. Note that the M8 bolts I got had the grooves on the backside so I didn't do any lock washers:
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Here is a close up of it bolted in:
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Here is both sides attached:
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Remounted my fishing poles without any problems:
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And here are some finished shots of it all strung up. It seems very solid to me. No wiggle at all. I'll be testing it out in a month when we do a multi-day camping trip where we'll be sleeping in the hammocks each night.
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Lastly, you may have noticed some yellow straps in the how-to pics. I added those as well. Available from any climbing store that has the bolt hangers, these guys are rated to a few thousand pounds and will serve as a back up attachment point. Here is a pic of me just holding one up. They only cost about $5 each.
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Originally, I was worried about it crushing the foam that surrounds the rear crossmember, so I tried threading it under that and then was going to melt another hole for it to pop through, something like this:
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I ultimately decided against that though because the strap moved around the crossmember too easily. Depending on how I was pulling the strap, it would've transferred that load to the fabric by pulling on the edges of the hole I would've melted. I don't want any stress on the fabric/zipper. Also, I decided the foam can handle its own and there's no real threat of crushing it beyond recognition. I did a simple test of wrapping the yellow strap around the whole thing and then putting my weight on it. The only sign of stress on the foam was this rounded over corner. My guess is it's the same stuff bike helmets are made out of, so it's going to take a large impact to crush it.
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With that decided, I just looped them around the whole thing. This way there isn't any force on the fabric/zipper and I can move them wherever I want.
Hope that helps someone! It was a very easy mod, whole thing for under $20, and could be done in less than an hour once you have all the supplies.