Excuse the 13 year delay but I just bought a Shadetree rest top and wish I had read your topic before. After reception, I installed it on my Sinclair base 3/4" shaft) which, I was told byShadetree would fit and it did. On,y problem; the top of the top wobbles and when trying to move the joystick up or down, the sides didn't move together, one side moved faster than the other.
I contacted the company and the told me to screw off the tension screws, remove the top and reinstall it on its Shadetree restop base. I did, nothing changed. I decided to screw the tension screws evenly till I felt about the same resistance and it worked BUT joystick was stiffer to move.
I have never bought something that didn't work and that the company tells you to disassemble part of it and reassemble it to make it work. On top of it, joystick is right under the rifle forend and parallel to it ! I am considering bending it so my left hand doesn't have to be right under the forend.
With the exchange and shipping it came up to over $600 CAD. Not impressed.