The trunk lid on my 2007 Camry Hybrid won't stay up when opened while the car is parked facing uphill. This is a real problem where I live when unloading groceries, etc. Does anyone know how to make the springs stronger?

You have put your finger on a common problem. I've seen people buy new springs and struts but they don't work for long. Most people I know just get a stick and cut notches so they can prop the trunk or lift back open.