Hi,
I would NOT mix Kevlar with Dacron. In fact I would never mix any type of bowstring material with an other. Because of different abrasion characteristics in the first place, but there are other things to concider as well ...
Kevlar is very low stretch material. If I am right, it has less stretch then FastFlight! Make sure your bowtips can stand that force!
If I recall it right Kevlar is sensible to UV light. It gets "brittle" and may break rather spontaneous. If you use it, then throw away the outer layers of yarn - just in case it was exposed to direct sunlight. I would do so with any string material BTW, if I can't be sure if it was stored right.
Kevlar is somehow "brittle" - even if not exposed to light and wears out rather fast. I think when Brownell came up with it a while ago, befor FF, it was used by FITA archers BUT replaced every 1000 shots!
The fibre is used in body amor. So why not hand it to your wife
"Darling, would you mind knitting me a nice bulletproof pullover from this ...?!"
and stay with B-50?
Falk