I believe the web page says it will support much more than 20lbs. I am also in the process of going with the HBL. Or may build a box, not 100% sure yet.
From their FAQ.
"
Our Homeboxes are designed to hold all the equipment you could possibly need in a Growbox.
You might not be able to hang your mother-in-law in there but, in any case, we wouldnt advise it, for several obvious reasons (even though you could control any odour problems perfectly).
Suggested maximum weights are:
Homebox XS, S, L, XL:50 kg / 100 lbsHomebox XXL:2 x 50 kg / 2 x 100 lbs
Make sure that heavy weights are attached to the centre top poles with the shorter hooks, so that the weight is evenly distributed on all 4 sides."
buy-the-homebox.com - universal indoor grow box kit