Justin,
Just to clarify that you with your vast jungle experience are making the following proclamation, that while 30+ seasoned infantrymen were freezing their collective asses off in the Panamanian Jungle, that if a single one of them would have been wearing fishnet clothing instead of BDUs then they wouldn't have been hypothermic? Yup. Sounds like holistic logic. You go ahead and run with that.
You know I think you're special sunshine. I just can't pass on an opportunity to bust your chops some.
One more time for the OP:
If you want, I can go to walmart, buy the cheapest/thinnest sleeping bag they have there and sew a jungle rated patch on it. It'll likely be rated to 50*F or so but these cheapie sleeping bags are rated optimistically so no guarantees that it will get you to 50*.
That's basically what a "jungle" sleeping bag is with the exception that some of them have a bug net sewn on them. That, in my opinion, is a fatally flawed design and here's why.
We all instinctively know how to stay comfortable in a sleeping bag when it gets warm out. Step one, unzip. Step two, kick a leg out. Step three, peel the bag off of you. Step four, etc etc keep making adjustments until you find the sweet spot.
Well if you have a sleeping bag with an included bug net sewn in, and that is your only system to keep the bugs and other critters off of you, your only options are to either zip up and suffer through the heat and humidity or unzip and get eaten alive. Here's another problem. The nights that you are most likely to zip up due to rain, bugs won't be much of a issue. The nights where you'll want to open it up and vent, the bugs will tear you up.
My recommendation. Get a lightweight synthetic sleeping bag; I never said or suggested a "mountain bag". Pair that with some kind of mosquito net that will work for your sleep system (eg ground sleeping vs cot vs hammock). Bring some kind of lightweight sleeping bag liner as well just to be safe.
I spent my entire time in the jungle sleeping on the ground because that was a tactical requirement. If I were to do this again for R&R, I'd bring a hammock. One of the liabilities of the hammock in the north that is a benefit on the equator is that air flows all around you. I've also stood on ground that was nearly knee deep in water an hour later. Being a couple feet off of the ground when this happens is also a good thing.
A cot has some of the same benefits. You are off of the ground so better air flow around you.
The USGI Patrol bag I previously mentioned is proven in this environment. I have hundreds of nights in the jungle with it. You can find them on Amazon just about any day of the week for less than $20.
http://www.amazon.com/gp/offer-listing/B0046JYNB8/ref=sr_1_1_olp?ie=UTF8&qid=1417200999&sr=8-1&keywords=usgi+patrol+bag&condition=used
Again, I sincerely wish you well on what sounds like a grand adventure.