Hi,
By your description it sounds like you have a 20x1 needle, which is a 1-11/16" or 42.5 mm. A photo of your machine would verify. I've seen new 20x1 needles listed on the internet and might be worth looking into. Can't say I've ever retimed a shuttle machine other than cheating the needle but I would think it's more complicated than lowering the needlebar. Guess you don't know until you try.
Jon