Great advice acakactinum! You just helped me get my first super-O! (I think)
I was on my side with knees up at my chest and I needed to stretch my legs out a little bit. So, I crossed my legs as I straightened them out and got a really nice sensation from this position. With my legs still stretched out straight and crossed I thought back to your post, I was thinking; "Wasn't that guy going on about something to do with clenching your thighs?" Literally 5 seconds later I get an extreme response and get the feedback loop in overdrive. I started shaking like crazy, my head going back and forth along the pillow and my legs still crossed and straight just moved back and forth just keeping my thighs clenched. It only last about 10 seconds but it was intense! I'm getting the shakes just thinking about it now. I'm going to have to try this again with something to tie around my thighs to get it to last longer next time.