Overnight parking near ostrander

[overheadx2]

My wife and I are headed up to Yosemite in a couple of weeks and wanted to do a quick hike out to Ostrander lake. We won't be able to get up there until late afternoon on Saturday and wanted to hike in Sunday / Monday. I looked for a campsite at Wawona, but there were none available. I have pop-up camper on my truck and could easily pull off the road somewhere but don't know where that is possible. Is it possible to sleep overnight in the trailhead or are they very strict.