Update: After having used this rod holder on several outings I have really started to appreciate the benefits it's design features provide. The locking system seems to be reliable and it certainly does a good job of maintaining position under use.
They can be coaxed out of position under a heavy strike (from, say, a shark) but with the locking system engaged, the rod seems nicely secure regardless. I have concluded, however, than when used with lighter rods and in stealth fishing situations, the Light Speed rod holder is better used as a simple tube (by inserting rod butt into on end and just sliding into the holder in a 'closed' state) instead of using the jaw locking system. This is because the locking system makes a bit of a clunking noise when operated - especially when snapped open with the rod - and has potential to spook fish. Due to this, the addition of rod leashes are still recommended.
While leaning down on one of my rod tubes at Fraser Island I achieved something that I always knew was possible, but unlikely to happen - I managed to lever it right off the ball mount. This occurred while extracting the rod to fight a fish and although inadvertent, wasn't as bad as it sounds. It separated from it's mount while being levered forward, not backward and I had a hold of it and the rod at the time. But it made me realise that by mounting the ball on the front of back sides of the crossbar, the crossbar itself can become a surface from which to lever from.
So in my determination to find the ideal AI crossbar rear-mounted rod system I started thinking about mounting the balls on the top surface of the crossbar. And immediately I discounted the standard tubes as a potential holder for a top-mounted ball, simply because they can be tricky for the ball and socket to maintain a steady grip. The main reason for this is that these tubes support the entire weight of the rod from the butt-end upwards, which is why they become top heavy. I figured that a rod holder that would hold the rod at it's intended balance point at the reel would be far less problematic. After looking into it more closely I became more interested in two rod holder types: the RAM Revolution tube and the newer RAM light speed rod holder.
I came ever-so close to trying a couple of Revolution tubes, which use a single ball socket mount and a simple moulded tube (similar to the 2008 tube) attached to it's mount arm by way of an adjustable ratchet. I like the basic utility this rod holder offers, but concluded I'd have to cut away the bottom end (to make the tube hollow all the way from top to bottom) to fit my rods properly, with the real seat positioned in the groove at the top of the tube. This would make sure the balance point of the rod was closer to the centre of gravity of the holder, and reduce potential for inadvertent ball/socket slippage. Of the two options I arrived at, this is the less expensive and also the one most likely to still be performing optimally a few years later.
The RAM light speed rod holder, however, is a newer product and one that I've been thinking about experimenting with for a while. This system uses rabbit-trap style locking jaws to clamp the rod in place, exactly at the balance point around the reel. This also means that when locked in place, rod leashes are not really required for these holders. The idea is that to release the rod from its locked position, one simply undoes the safety lock and then pulls the rod upwards to break it free from the jaws, hence the name 'light speed'. At first I suspected that it might be difficult to use these on a kayak while seated but once I actually fitted one to my kayak and tried it I realised it wasn't terribly difficult at all. And getting the rod back in wasn't too hard either.
Mounted to C sized balls clamped to the rear crossbar (facing upwards) the holder sits a little higher than my 2008 tubes and I can position them at similar angles. After testing them out in open water on the weekend I was also pleased to discover that there were no slippage issues at all, even with the rods pointing out at 90 degrees to the hull, level with the waterline. While I didn't manage to hook up to see how they'd perform when loaded up, I suspect that while they may slip a little bit, they certainly wouldn't slip as quickly or as far as the standard tubes. I may be on to a winner here. They felt great to use on the water and gave me more confidence in the security of my rods. Until I've hooked a shark, tuna or some other pound-for-pound bruiser I can't say for sure, but the experiment is off to a great start. I used RAM 271U-2 RAM Mounts to fit them, otherwise known as a RAM C size 2-2.5" rail mount. These suckers aren't cheap, but are very solid and the only reasonable means of attaching ball mounts to the new Island crossbar design.
I did consider both the Revo tune and Light speed holders that use bulk head mounts as well, but concluded that while these might work well for other kayaks, not so well with the AI. That is because the crossbar gets in the way of the best mount positions, as well as the fact that they have less pivoting ability (which is both good and bad, depending on how you look at it).
Update: They seemed good to begin with but the more use they had - and the more big fish and sharks hooked while using them, the more their performance suffered. The lock arm failed on me a few times and under heavy strike these holders would get pulled over backwards. I think these would be fine for most kayak fishing scenarios, but not great where big fish dominate.