Hi CactusMatt, hi folks.

I suggest that you take the time to view the video tutorials to get acquainted with SketchUp (SU).

It is more capable than you think in making this very simple design.

Believe me, the few hours taken in viewing these videos will save you a lot more hours of frustration when using SU.

In the mean time, here is a reconstitution of your pannel, using some assumptions. Click on the scene tabs of this SU file for ideas.

Panel-Loc extrusion profile - JL.skp
If you save only the final extruded panel, you will see that the size of the resulting file is 20K.

Best regards.