Ummm....well what I know so far is that any kydex thicker than .125" can indeed stop serious sword blows. Won't do squat for bullets though, unless we're talking 22short.
Basically, if you used kydex armor on the legs and arms and the *very* best ballistic armor on the torso (modern grades that at least resist blade penetration, some do these days) you'd have quite the combination. Not street-practical if we're talking about trying to get "Medieval-knight-grade" coverage. BUT I've worn quite comfortable plastic elbow-forearm and knee-shin motorcycle armor pieces for entire days at a time. The knee-shin bits can be worn under ordinary jeans and don't look odd until you sit
- even then, not too noticable. The elbow/forearm bits are worn under a jacket and again, not noticable. Both are retained with elastic/velcro straps.
I crashed a motorcycle once at fairly high speed wearing such. Mebbe 50mph, rolled for about 75 feet, got up literally without a scratch. When the CHP finally showed up, they couldn't figure out why I was fine (and working on my bike), until I took my jacket off revealing the armor. These were bike cops, and one said to the other "hey, Garcia could have used that stuff last week!"
. An elbow piece was deeply scratched, and one of the knee cups was cracked right down the middle...I wouldn't have walked away from that one without the armor. I also had interlocking plastic plate spine armor but that wasn't a factor in this particular wreck.
Those were in high-impact plastic that a Khukuri could probably cleave but the same stuff could be home-brewed in heavy grade kydex quite easily. You could raise your forearm overhead and stop an overhead blow from a saber, khuk or similar and it would come as a total shock to the assailant if you had a light jacket on concealing the armor. Use a layer of 1/4" neoprene foam underneath for comfort and padding...or yes, in theory you could use a layer of ballistic kevlar under the kydex for padding and bullet protection but then weight goes up, flexibility down. Plus it might get a tad hot.
In each case, the elbow "cup" must be separate from the forearm piece and linked with straps. They can overlap a bit but they must be separate for flexibility. Ditto the "knee cup" and shin piece.
The plastic motorcycle crash armor I've worn had zero effect on mobility. .160 grade kydex would be slightly heavier, but not enough to matter so long as the coverage area was LOW. You'd have the ability to shift the hidden armor to meet an incoming edged threat, whereas on the medieval battlefield they were trying to stop arrows addressed "to whom it may concern"
.
Also available from better motorcycle shops: leather gloves with hard carbon fiber armor across the knuckles (whoa!) and fingers. I don't think I need to elaborate on the potential offensive capabilities
. As defense against a sword/knife to the wrist, not so good...you'd have to add kydex panels in "plate form" against the backs of the wrist/hand to retain flexibility.