Pilot,
JLG built cat? yeah i've seen a few of these, just don't make the mistake of thinking you can just order JLG parts from their version of this machine, they don't always fit because of CAT's proprietary design in some cases.
But that's a whole different story we won't get into now.
As for that Product Bulletin from JLG?
i would highly recommend doing it.
JLG generally pays for most everything in these product updates so why not?
They may not cover hauling charges but that's nothing compared to the cost of the repair.
Look into it and you'll see ;o)

Here is the update the Customer does not want this modification but with more research there is a update from JLG service letter reference: Cat 1203 publication date September 23, 2013 (revised October 4, 2013) it requires boom structure enhancements adding anti kick valves to the compensator cylinders pn# 353-3455 this a major repair requiring to air arc the pin bosses off the boom and weld new ones on you will have to remove the boom or risk the machine catching fire.

I have a customer TH514 with the same issue the customer claims they broke the pins 3 times I have a call out to Cat no response at this time, I will keep you posted on the response, it seems the weak point is at the retainer bolts that go thru the bosses we checked pressures at the barrel and rod ends at relief 3,500 psi. if I don't get a response from Cat I think the solution is to get a pin long enough to go thru the bosses and don't drill a hole in the boss for the retaining bolt just have the end of the pins drilled for oversize washers just like the boom pin on a excavator I will keep you posted if this works.

I realize this is an old post but i figured I would share my experience with this anyways as it happened recently to our TH514C

We have had this happen twice now. Once the eye on the end of the cylinder actually ripped apart and the other time thankfully the cylinder was put incorrectly and was able to slide off the bushing. In our application the operators are used to running a JLG and they always drive around with the attachment tilted up all the way. So if you have the boom up and the attachment tilted all the way up and you go to let the boom down the two compensation cylinder can't compensate and tilt the attachment up farther while you lower the boom. It seems there is no bypass valve or it doesn't work fast enough and over time you will end up with a catastrophic failure. We have mandated that the attachment whether it be forks or bucket etc should remain level as much as possible to allow for the compensation cylinders to do their job. I think the biggest issue is lifting and lowering the boom with your attachment tilted all the way up or down. Seems like a really bad design and I did talk to a CAT Engineer about it. However the machine now is too old for them to really care about it anymore. Hope this helps some more people with this problem