The original Tenax studs that Triumph used for the windscreen had shorter length threads then what's available today. The longer ones sometimes cracked the glass when screwed in, hence the addition of the nylon washers. The washers I'm using measure about 0.030". Here's some info about it from Moss...
https://www.mossmotors.com/graphics/products/PDF/802-998.pdf
Randall,Looks like Moss doesn't sell the washers separately, at least the number in that tech note doesn't match on the web site. These should be a good substitute
https://www.mcmaster.com/?m=true#90295a414/=152w0pg