Congratulations, Lousyreeds1 ! Your arm replacement seems to have worked out very well.
When you use the template, remember that although you will be using the cartridge sides as reference points, in fact it is the stylus cantilever you are aligning. If all 3 are parallel, that's perfect, but in practice they are not, sometimes.
There's no reason not to go with ordinary stainless washers. The fewer the better, so if you can get different washers of different thicknesses, that may come in handy.