Happycat, stick with the Stimpson GS eyelets. For Kydex/Concealex work I don't think you want to go any smaller the GS6 sizes. Right now I only use the GS6 size and they seem to work pretty well for small and medium size sheath (approx 5-6" blade length and smaller), but I only have a plier die for the GS6's. I have seen larger sheaths made with GS8 eyelets, I also have a couple of Mike Satre's neck sheaths that look like they are GS7 or GS8's. As for the length this depends on the thickness of the material and how many layers you are trying to crimp together. I have .080" thick Concealex and the GS6-6 (.187") did not give me enough material to get a good roll to hold the material together, but the GS6-8 and GS6-9 gave a good hold and a nice roll (the GS6-9 may be too long if you don't have a piler).
Generaly I think a good rule of thumb for eyelet lengths is to get them a sheet length to a sheet length and a 1/2 longer than one sheet of the material you are working with.
Example 1: .080 " Concealex
2 layers = .160"
add .080" for length needed for eyelet(thickness of Concealex)
.160 + .080 = .240 ,aprox GS6-8 (.250)
Example 2: .060" Concealex
3 layers = .180
add .060 for length needed for eyelet (thickness of Concealex)
.180 + .060 = .240 ,aprox GS6-8 (.250)
Keep in mind the tolerances for Kydex/Concealex can vary and you can get stock as thick as .065 or .085 and that adds up the more sheets you bond together. So that's why I say you might need to add another 1/2 thickness of your sheet to the length of the eyelet (.060" thick add .060 plus .030" more).
Sorry for the long winded post I wasn't sure how to explain the sizing or if I explained it well. If anything is unclear I'll try to clarify. Now I don't do that much Concealex work so this is just what works for me on my knives/sheaths. Normark has done more sheaths than I will ever do and he might have something to add.
Take care,
Tom
[This message has been edited by Tmac (edited 04-05-2000).]