Before you go to all that trouble, try calling Wolfgang at Advanced Machinery for some Q & A. He is very good about helping find your problems. It really sounds to me that you have a part that is either loose, worn out or broken. The Hegners are not a "shakey" saw if mounted correctly. In fact, there is a video on Youtube where a guy buys a brand new one and unboxes it and sets it on his workbench unbolted or clamped. He runs it and it is very smooth throughout the who RPM range. So, there has to be something wrong with your saw. I had one that was mounted on the factory stand and it definitely had it's sweet spots but I could run it full open or anywhere in between and it was useable. It's important to make sure the bushings in the arms aren't worn and properly lubricated. Also, there is a link that fastens to the motor flywheel and connects to the lower arm that is famous for breaking/cracking. I had to replace mine. Call Wolfgang. It might solve your problem.
https://advanced-machinery.myshopify.com/pages/hegner-home