I've tried PU/PD to extend her naps, but it seems once she's up, she's up. She's a spirited baby, but her naps have always been erratic- usually 30-40 minutes, then 80-90 minutes every few days. I can never predict when she'll take a decent nap, and after a month's worth of nap data, I still can't figure out why she sleeps longer occasionally.
I've also tried W2S, and applying pressure before the jolt, but neither seems to work.
It also seems like if I try to put her down before it's "time" for a nap, she fights it. She will only take 3 naps a day, no more- so even if she needs more than 3 naps, even if they're each 38 minutes, she won't take another one.