We got tired of seeing sagging coroplast under the front half (drop-frame) of our RV. We even had one section come loose on one side at one point and had to re-attach it.
To fix the sagging and provide better support for the insulation under our RV, we used 1" angle aluminum from Lowes as an added support mechanism. I cut it to a length to fit just inside the LED strips and bolted it directly to the frame using self-tapping stainless steel bolts. I pre-drilled holes in the angle aluminum and made starter holes in the frame.