Supporting P trap for shower under floor

[sandyman720]

Well I made the stupid mistake of not supporting this shower p trap and my subfloor is already down. About 4" Under the p trap there is a piece of plywood so there is a solid surface. How would I go about supporting this now without pulling up the floor. I am using a Wedi pan and I thought they would have the drain glue to the pipe like Schluter but I was mistaken. I don't want the weight of the drain/trap pulling it out.

1- feed 2x4s thru hole and some how stack until they are under and supporting the bottom of the trap

2- put some kind of strap under the trap and come back up thru the hole and screw into subfloor.

Thoughts?!