Yep, 2 bolts. Seemed to work OK on the previous version as well. I tend to "spin", so there's perhaps not as much pressure on the thing as would be the case with someone who mashes the pedals.
The guy with the site I stole most of the original design from cut slots in the boom and secured it with radiator clamps! Didn't look sturdy to me.... I plan to study the thing a bit more this weekend and see if I can't get a yet-more-efficient chain routing.