Mostly all cayenne varieties are thinner flesh allowing them to dry quickly. Jap's flesh is thicker, do you dry whole or half pepper which would give you more surface area to dry better.I pickle my excess jalapeños in a red wine vinegar/salt/pepper/sugar solution. They never last long enough to be anything other than refrigerator pickled peños.
Drying in the dehydrator works awesome for cayenne, but never had good results with jalapeños. Not sure why...