Wow! Thanks for getting me motivated to build something very similar based on those plans.
Unfortunately, the beam is currently indoors, so I run boom-less just hanging the elements from the rafters and letting gravity keep the wires straight.
I am also using an unconventional driven-element dipole, which consists of a quarter-wave wire attached to the center conductor of the coax feedline, and for the other side of the dipole, I use 4 ferrites (Radio Shack 273-105) snap-ons a quarter wave AND at a half-wave point down from the feedpoint. This way I'm forcing the common-mode of the braid serve as the other half of the dipole. The feedline serves as part of the bottom half of the dipole and the feedline itself.
(Normally instead of using a coil of coax for a choke, I like to use 4 of the type-43 ferrites right at the feedpoint, but in this case, I purposely move it down a quarter wave to emulate a wire. Makes an interesting alternative to a j-pole driven element)
I'm still playing with the reflector spacing since I'm using 75 ohm coax, and hope to switch to 50 ohm soon. But for now, the results are good, so thanks for publishing those specs!!
This is the first beam I've built, and now you've got me hooked! Must make one for real outdoor use however...