When the chassis is sitting on a level board (pic) most times the bubble will be off right center (I have three chassis and they are all to the right center) I used a bicycle wheel strap(rubber that shields the tube from spokes) which is about 30k thick I punched out two pads using a paper punch inserted them on the right side under the bubble not the clamp side as you can see the chassis is level..
It does not matter where the bubble is as long as its the same place where you level the scope to with plumb bob When you shoot.
It does not matter where the bubble is as long as its the same place where you level the scope to with plumb bob When you shoot.