I only want add that there is an adjustment at the lens stage if it is a late enough model; if you don't see the adjustment screws as indicated in the attachment, then only shimming is possible.

I own the Saunders 4550XLG (i.e., 7452), I think the 7451 (which is the Saunders 4500II) has the same lens stage adjustment as the 7452, again, if the model is late enough. If you have the screws, and it requires adjustment, be sure to give KHB a call, they give you the precautions.
Cool, thanks for that information!