Bill Tindall, E.Tn.
The first piece I made with a recessed side panel I dovetailed in the top rail into the leg, then M&T the panel and bottom rail into the leg . It was a fitting nightmare and I realized after entirely unnecessary.
In this case the panel is M&T into the leg which supplies all the strength necessary. The top and bottom rails are dadoed and fitted over the edge of the panel, a vastly more simple fitting. Fitting is done by shaving bits at a time off the ends with a shooting board until the false rail slides snugly between the legs.
So to add a rail to the bottom will be trivial, except, it will lower the side by5/8" +/-. This addition will lower the side below the drawer rail in the front. I will make the addiiton, dry fit and see how it looks.
Also I realized the panel sets in to much. The shadow is too pronounced. This too is an easy fix. I'll mow off 1/16" from the outside of the legs. I considered making them this much smaller in the start.