I would not clamp it, at least not until after a week or more for the paint to harden, I could see paper-towels or kleenex leaving a mark in softish paint. And with that gloss, anything will show.
Maybe another day in the sun could return it to normal, at least part way? I do not know if plastic has a "memory" like sheetmetal can.
You may have luck even with it bent/splayed like that. Glue one rocker panel in place leaving the other floating in space. After 24+ hours of hardening maybe the other side can be pulled in and glued with only a little bit of clamping force.