I’ve been using a Klassen for almost a decade now, so I think I may be able to chime in here and add a little of my thoughts, as one of their die-hard supporters. I always am of the camp of trying to find every kind of vest that will fit you, and letting your body decide what works for you. But on a less empirical and more theoretical level, here are a few thoughts…

I got the Klassen because simply I could not operate with a front mounted vest. I’ve never known myself to have “back issues”, but the front mounted vest gave me real problems. I’ve tried many a vest, ranging from the Model 2 vest I started with to ExoVests, and I’ve never found one I can comfortably fly with. My back muscles tense up immediately, and even flying a lightweight sled for a few hours in a single day of workshop teaching a couple of years ago was bad enough for me that my wife had to help me out of bed the next morning. For me, the Klassen vest was a survival technique. 

The primary difference between the Klassen and a traditional front-mounted vest is the reliance on your shoulders to carry weight. In the Klassen, you can actually unstrap the shoulder straps and the vest will still carry weight (though it’s not recommended to fly this way, obviously!). The straps serve to keep the vest from sliding down your body, or moving around on your hips when the weight shifts – they don’t carry much of the weight of the rig, only a few pounds. The weight holding up the rig is clamped directly into your hipbones, and transferred down into the larger muscles in your back. There is a small amount of force pushing at the top of your back to resist forward forces, but being mounted to a completely rigid structure allows that force to be small. What this all means is that the muscles in your back which must tense to keep your spine upright are significantly less taxed, and for me, that means I can operate.

The removal of those back muscles also tends to lead to an increase in longevity in the rig for many operators, and I’ve known that myself, at one point doing a continuous 4 hour event in the rig with a fully loaded sled without breaks. I’ve also flown incredibly heavy rigs, including an Arricam LT on the Wave with a 6×6 gyro on an M1, and had no issue handling the weight. Hell, Larry flew his insane double-Alexa rig on Hugo with a Klassen! 

As for how it changes your operating, this is the big thing I’ve taken away both from my testing and my talks with Larry – the Klassen is locked to your hips, and therefore anything you do with your hips will translate directly into the socket block. A traditional front mount vest is connected to your entire torso, so it is able to “average out” any hip movement. So, basically, if you walk carelessly with a front mount vest, you have a much better chance of your torso being relatively steady than your hips. That little bit of hip sway inherent to most people’s walk will translate through the arm at certain speeds, and it will lead to more sway and translational speed changes in your moves. So, if you have a front mounted vest, theoretically you can get cleaner work than you could with a Klassen. However, with some training, it is absolutely possible to do incredible work with the Klassen, as can be seen by some of the operators who wear it, including both Larry and Jim McConkey. I’d dare you to say that either of their work is “lacking performance” because of the vests they use.

Doorways. As is obvious, I am a larger man. My shoulders are wide, and my vest therefore is one of the larger ones Klassen has ever built (I believe my first harness was the 2nd largest they had ever made, if I remember right!). So, yes, I occasionally have had clearance issues with my vest. Mostly, these clearance issues involve the fact that I am now surrounded by a hard, solid, and at points even pointy bit of structure. Backing into a wall now leaves marks! Barely sliding through a doorway now takes off paint! For most people I’ve seen, the carbon arm sticks out about as far as their shoulder (even less than that for me), so that is less of an issue than the back of the harness being solid and sticking out several inches on your back. If you find yourself with your back against a wall often, the Klassen’s size in that regard may not be kind to you. And if you do have to do a shot squeezing your shoulders together or going sideways to fit through a door, the Klassen will probably cause issues. But I’ve had very few problems in my 9+ years with it.

But I will say this – with the Klassen, you can easily throw the rig out in front of you with out pain, which does make it very easy to get through tight spaces with the rig, or operate on the wrong side, or throw the rig around for super kinetic moves. I also do find that the arm curling around the front of the harness keeps it out of the way, allows for easier visibility of the monitor (a huge deal, and it seems insane to me how little I can see of the monitor every time I try on a front mount vest), and generally seems to work well.