I've had my G-Belt up and running for about a week and a half now and it's a pretty cool piece of kit.
Ordered (in the UK) on a Tuesday and it arrived on the Monday so very efficient service from Simxperience it has to be said. As anyone in the UK who's ever bought anything from the states will know, you will end up having to pay FedEx around 22% in taxes and import duty. Final price for me was around £960.
I'm not using any other form of motion (and have never even tried any), just SimVibe chassis on all 4 corners of my rig. I race 100% in VR and play AMS2, iRacing and Assetto Corsa.
I just mounted mine directly onto the back of my fiberglass racing seat using the supplied screws. I didn't bother with the template (don't have a printer) but you don't need it anyway. You just need to mark a centreline between the belt outlets on the back of your seat. Then get the G-belt unit to a height where you can see your belts will exit the belt outlets on your seat at their widest point into the G-belt unit. Then mark where your drill holes will be. It uses 6mm bolts to attach so I used maybe a 5mm drill bit (not totally sure but better to go small and then realise you need to drill a bigger hole than the other way around). I was able to remove the cover of my seat which you'll need to do if you're mounting it this way. It fits pretty securely. Inevitably there is some give if you press it on the sides but not too much. I had a friend in my rig with it on and couldn't detect any side to side movement when they were going through corners. I mounted it on my own but I would say this is a two man job. The unit is very heavy. A couple of things to note, it comes with a US type plug on the power cable (kettle type) and the USB cable (type A to type B) from the control box to plug into your PC is very short. Fortunately I have plenty of spare cables lying around so this wasn't a problem for me.
I'm using a 3 inch 6 point Sabelt racing harness with shoulder pads (you can get these off ebay new for a reasonable price). It's attached to my 4080 rig using M8 eyebolts into t-nuts (making quick adjustments easy). I don't use the central belt hole on my seat for the submarine belt. I did find that slightly uncomfortable. Instead it's mounted under my seat and then the straps just go over the top/front of the seat. The two straps are mounted quite wide apart and if I pull on them when it's attached I find it puts pressure on the inside of my thighs rather than my... you know what
Setup up is pretty simple (plug and play really). There's no instructions in the box but they're easy to find of the Simxperience website. I already had the simvibe software installed and the G-belt didn't show up in SimCommander at first, but when I updated my licence with the new one provided when you buy the G-belt it then showed up (presumably this is a full SC4 licence rather than just one for simvibe).
Out of the box it's very impressive. It does what you would want I guess. Really makes you physically feel like you're breaking into corners. As for side to side cornering g-forces. I found these quite subtle using the default setting so turned it up (still experimenting here) and that made it much more noticeable which I like. The only thing I've added (the default effects are breaking, cornering, acceleration and bumps) is gear change. I also found when I set the profile to 'extreme' that the bump effects were more in sync with the bumps coming from my simvibe than they felt with it on the default profile. Again though, still experimenting. I'm currently running with:
Breaking 95%
Acceleration 50%
Cornering 85%
Bumps 55%
Gear Change 100%
Early days though and I'm currently just testing out lots of different settings . Would be interesting to hear what other people are finding works for them. I will probably end up going with less intense settings I reckon as I'm probably just trying to get short term extreme sensations out of it right now for the fun of it.
I'm happy with my purchase. It's not cheap but it really adds to the immersion and the sense you're actually in a real racing car!