First images here include the side panels being cut. My dad and I worked together with the rule of double-checking each other's measurements. The great part is that I made a few mistakes that he caught and I caught some of his... so going slow and measuring twice (and sometimes more often) definitely paid off and we made all the cuts correctly the first time and I didn't have to invest in more than the original 3 sheets of Sandiply.
Speaking of sandiply - this stuff was great to work with. Not too heavy. EXTREMELY smooth on the "good side" and DECENTLY smooth on the "bad side." There were ZERO snags/splintering of the edges and all pieces were flat and no warping. I've not worked with warped plywood before so I can't speak to how much work this might have saved me, but I can tell you it made measuring and marking the cutouts much easier.
In one of the images you'll notice that we clamped two sheets together. "Good sides" were placed together so that when we cut out the side panels they will be mirror images of one another and I can use the smooth side. This also saved time and I only had to draw one side panel on the wood. We used a circular saw set to 1.75 depth and it cut through both sheets easily. No sanding was required to "match" the sides. That said, it was very helpful to have two sets of hands and eyes to do this.