Bah. Kydex scraches stuff, gimme a break
Sheffields supply sells 3/8" neoprene, get it. Lasts forever, nice tight mold, too. dont get that 1" foam they sell in their catalog, it burns and melts and doesnt get a good mold. Use a heat gun, and gloves are a good idea, i think Allen Blade uses cotton gloves because they dont hold the heat like leather does. I glued the neoprene to some 3/4" pine boards and stick it in a vise and crank it. As for measuring it out, I just eyeball it, and then trim it down to size, kydex is cheap enough

I used 1/4" eyelets, so paracord or bead chains go thru it easily. Just get an eyelet setter, it helps a lot.
As for scratching the blade, I dunno. I have HP (1500 grit hand finish) blades in kydex sheaths, and havent had one scratch yet. I dont even use tape anymore on the blades. I just use that neoprene stuff, and it don't form tight enough to scratch it. I think one of the probs is that people like those really tight, crisp sheath lines, which means the kydex is RIGHT on the blade, and will cause wear. You can see the outline of the blades on my sheaths, but I dont try to get those really sharp lines, because sometimes, it makes it hard to draw, and reinsert. I'll get some of my kydex sheaths scanned in a day or 2 when i get my scanner set up, and show you what I mean.