I can say that I've never been bitten through the fabric on my Explorer UL, even before I started using permethrin. As to whether that's due to the fabric or a too-small statistical sampling, well...
Hope it helps!
"Just prepare what you can and enjoy the rest."
Most are fine with 'thrins. I have not found a claimed odorless one for indoor use which really is odorless and not obnoxious, for me, even days after application. Hence my curiosity about picaridin effectiveness applied to the hammock bottom. Coleman packages it in (refillable) 1/2 oz mini-cigar spritzer containers.
Of the half dozen hammocks I've had, only the Clark hammocks seem to prevent mosquitoes from biting through the fabric. I've had HH, Mosquito, War Bonnet Traveler and Black Bird, Tree to Tree Trail Gear Switch Back, and a few others. In almost all cases they were double bottom, 1.1 oz fabric except for the Clark and HH. Almost all of the time I've had a closed cell sleeping pad, which of course, they can't bite through. They do sometime get in under a under quilt, but not often. If you want to test out how your hammock does with mosquitoes, come on down to Florida during the spring, summer or fall.
I wouldn't spray any hammock with Deet, it will melt the fabric, which in time will fail, leaving you on the ground. Never tried permethrin (or anything else), I'd be a little worried about it getting into your blood stream if you were in contact with it all night, every night.
Another poster mentions fabric forced such as 70 denier nylon used for the Hennessy UL line. It isn't so much the fabric thickness as the tightness of the weave. The Hennessy Hyperlights and Deep Jungles, for example use 30 denier nylon with a Spectra grid. Thinner and lighter fabric than the 70 denier used in the UL models. Both offer far better bite protection than the rather open weave fabrics used for the Deluxe models. Personally, I spray all my hammock bodies, packs, sleeping bags, and clothing with Permethrin. Of course, I'm in MA where we have been battling Lyme, West Nile, EEE, etc., now so bad as to be nearly public health crises.
The upside of the more open weave Deluxe fabric is greater breathability and coolness.
Hennessy Hammock afficionado and supporter.
I've heard of people getting bit through their hammock before, but I didn't experience it until last month when I camped on the edge of a swamp. The night prior I had shifted my Super Shelter off to the side because it was incredibly hot where I was hanging. Once climbed in the next night and started to feel the biting, I had to jump back out and put the SS back in place. That should have been enough of a warning, but it was not. My foot end was a little higher than normal, pushing my head closer to the end where it brushed against the bug net. In the morning I had mesh-patterned bites across my forehead and along one elbow and knee. I've been hesitant to use permithrin, but that experience definitely has me considering it.
I use a 2QZQ breathable UQP during the summer months and it provides just the right amount of insulation and air circulation and has the added bonus of keeping the Mosquitos at bay.