I strung up my guitar from 9's to 12's (extreme difference I know), and I only have two screws behind the back plate that are securing the bridge, so the bridge is at a very high angle. Is this safe?
Re: Bridge Plate Angle. Help! Its raising the roof
You need to set the 2 screws behind the plate deeper into the body. This will increase the tension on the springs pulling the bridge back down. I would start with 1.5 turns on both screws to start and then retune the guitar. As the bridge starts to come down you will want to use smaller turns on the screws until the bridge is in the proper position. Re-tune the guitar after every adjustment to the screws.
Re: Bridge Plate Angle. Help! Its raising the roof
Just tighten the trem spings (or add another one), retune, tighten, retune....until the setup is right again. Then check the intonation and if necessary re-intonate