I don't use one, actually: in the studio I'll usually just use a c-stand and grip arm for the Mola or even the big octa. The only time I use a traditional boom is when I need to really extend something out or boom it overhead, in which case I use an Avenger A600. I'll also take that out on location if I'm traveling by road and packing the whole grip bag.
I got a canvas-like material art protfilio bag that fits the 24X30 sheets of foamcore really well. I can put 6-8 sheets of foamcore in the bag and it is easy to transport. The local art supply house had some that were scuffed a little that they were selling for less than $10. It has a piece of masonite in the back to stiffen up the bag, has a few handles to help carry it around. Actually per reflector it takes up less room than my folding disk reflectors.
A question I've had for ages is: does the 96" version share components with the two smaller versions, or is it only the 72" that almost gives you two sizes in one?
They all share the same components. If you get a 96" version, you can make a 72" or smaller. Before you buy, check which set-up is the cheapest: the 96" or the 72" with two extensions. From time-to-time, I've found one's a better deal than the other!