I also found something else that works well, and is much less expensive. I was at Target looking through the racks, and found a skirt very much like my "exerskirt"; it was a similar material, and even had long shorts underneath. I thought to myself "there is no way that Target is selling a modest running skirt!" As it turns out, it's actually a "slimming skirt" because the shorts underneath are supposed to slim you. It works quite well as a running skirt, though. The shorts underneath are see-through so don't contribute to modesty, but they do keep the skirt above from chafing or clinging, and they are cool. It's quite comfortable.
It's longer on me than on the model--mine covers my knees.
Only downside is, no handy-dandy little key pocket, so I have to hold my key in my hand as I run (can't tie it into my shoelaces when I don't have any--but that's a subject for another post).
I still don't think that a woman should have to wear long skirts while running--I think that a woman can run in other things without compromising her modesty and femininity--but I am now persuaded that a woman can run in skirts. If that makes sense.