I actually asked Peter to do the asembly with minimal clamps as we get asked all the time " what is the minimal clamp requirement" .... a lot of folks don't have clamps and have to go out and buy them.
On top of that, the design really doesn't benifit from additional clamps as the side panels are located via dowels/dado's, you can't squeeze them together any further. With triples or quads, you'd obviously need 2 or 4 more respectively across the a braces. I guess if wanted, an additional clamp could be added between the braces and top/base but, it's not necessary, that's 1.5" MDF, the 2 in the center pull everything together nicely.
OTOH, as you know, one can never have too many .
And, those parallel Besse's do a great job of clamping across those braces
jay