This is another page that has nothing to do with dogs. It does have to do with my search to find a supportive brace for my trombones to help my tired limbs to hold the heavy instruments over longer periods of time. Hope this helps you.
I have or have tried almost all the available braces.
Hagmann hand support
Rath hand support
ErgoBone - was excellent for me at the time. Takes all the weight off the left hand. While using it, I heard that when that tension is gone, how free my tone can be, so that became my measure of how free my left hand was with other supports. But it made my Yamaha 822g very nose heavy, so I bought 2 counterweights, which mostly helped. Rather a nuisance with mute changes and I found it difficult to achieve micro-movements in angle face-to-horn necessary for accuracy, especially setting on. When I stopped using this, I also took off the counterweights.
Trombone Stick - a product similar to the ErgoBone, also in concept, but instead of resting in a harness, it rests on your knee. The trombone sits on top of a spring. It didn't work so well for me, because you still need to somehow keep the trombone from bobbing around on that spring on top of the stick. This still caused a degree of tension in my left hand that was very difficult to counter, especially further out than 3rd position.
Rath hand support and Hagmann hand support: Both were impossible for me to adjust, that they supported the weight without slippage and without unpleasant pressure points on the back of my left hand. Hagmann gave me a 10 day trial period so I was able to send it back. It's more configurable than Rath, but it was too small.
Get-A-Grip - Sheridan Brass - I wasn't able to bend it to a position that worked for me. I'm not a tool sort of guy and the metal wasn't so pliable.
Ax Handle: Mr. Olsen tried his best, but it just didn't work with my horn. The balance point is too far forward, which made the instrument very nose heavy and the attachment clamp is too thick to go optimally on the brace.
Curtis thumb rest – similar to the Ax Handle/Bullet Brace, but attaches to the trombone on the body just below the valve section to fit under the f-trigger. But on my Yamaha 822G the balance point was farther forward by the slide grip, so this made my instrument VERY nose heavy and demanded I counter this diving ... with the left hand. Like the Ax Handle, it then didn’t really support much weight at all.
NeoTech: Comes the closest to what I need. Not easy to adjust, simply because you have so many possible positions. But it's working now for me. BUT ... the velcro attachment points tend to want to open if I don't periodically give them a squeeze to make sure they sit well. It works best on my bass bone when I use the Yeo hand grip, but on my tenor when I use the tradition left hand grip.
Especially with the NeoTech, but also with the Rath and Hagmann, they do not relieve all the tension from the hand-lower arm-shoulder, but do so for much of it. I've found that approaching it like weight training has been a huge help. No problems getting through rehearsals and concerts as there are enough pauses to take the horn down and straighten my left arm. But when practicing, especially longer etudes, where you're in playing position for minutes at a time, I play until I begin to feel an ache in my left shoulder, then I play for 10-15 seconds more and ... take a break for 30-45 seconds. This regenerates the muscles and I can continue. I don't try to play through a lot of pain, but simply push the edge of the envelope. I also go to the gym twice a week and do exercises there for my wrist and forearm, but also shoulder. All this combined has improved my strength and stamina. Even at my age of 65, it's still possible.
The NeoTech hand grip is the one that works best for me, but your mileage may vary.
Yamaha 822G bass trombone
Rath R400 tenor trombone