I have a Canon 400d ( rebel XTi ) and a Sigma 10-20mm lens, I cant mount the lens on the top arm at the spacing recommended i.e between 93 and 99 depending on focal length. because the lip for the lens hits the Nodal Ninja arm and the lens ring (to change the focal length) also presses against the side of the arm
please see the photo attached to explain
Any suggestions on what I need to do to get round this problem ?
Marco is right - you do need the Camera Mounting plate (N-CP1) with this lens. You could also use the t-20 t-adapter but I believe the CP to be a better choice. Do NOT mount and use the camera/lens as you have shown in the image - you might damage your lens.
Touch bases with me off site - bill[at]nodalninja[dot]com. I have a used t-adapter I can offer you for free.