I love this. I would recommend having a dedicated upright and have it in a position where you don't need to move it up and down. I have mine in a position that allows me to do everything I do with it, pullovers, preacher curls, leg extensions, lying hamstring curls, etc and don't ever have to move it. There is a little bit of flex that comes from rack movement, which I've mitigated with the stand attachment that bullet proof offers. I don't have the space or budget for a lot of machines, this gives me the flexibility to replace a lot of machines with one rack mounted attachment. The pads and attachments are overbuilt and therefore heavy, but there is no doubt on quality for me. People who don't like to fiddle with settings will not like this, however. I've used my whiteboard to note best positions for my lifts so that I can easily get to where I need to. The main thing is to ensure the joint you are moving is in line with the pivot point of the isolator and then it'll feel very natural.
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