[bpape]

For some reason I can't get that link to load for the product you're going to use for the riser. In any case, there are a couple of things to consider.

If the riser is fully enclosed, it will need to be filled with insulation to prevent ringing. The top can't act as a panel absorber because it will be damped by the furniture. The sides might do a little something but you don't know what due to it likely being relatively short and stiff.

Now, if you use something where the sides are open and the top is solid, then absolutely, it will act as a broadband absorber - still needs the insulation.

Bryan