WB6BYU: Thanks Dale for the calculator!
W9FIB: We have access to a TIG welder. The aluminum boom will have two plates welded to it: one for the reflector, one for the driven element that makes mounting a snap. The driven element plate is actually a 2 piece (one for each side of the driven element). Here's an interesting manual on TIG welding with mention on techniques for 6061 aluminum:http://igor.chudov.com/manuals/Miller/Miller-TIG-Handbook.pdf
thanks all, 73, Rich, K3VAT