Hi Mitch,   Thanks for the info.  That jives with the documentation I got from Joe that says the tubes should be 35 1/2 inches.  The cap, by my quick measurements, adds about 1/2 " (maybe 9/16ths).  For some reason the spreaders on my boat (just the tubes) measure 34 and 35 inches.  Not sure how that happened.  At some point I'll buy new tubes, but at the moment I'm having an internal debate about whether to just cut the one down to 34" and sail the boat (and see if there are any surprises) before buying anything much else.
Cheers,   Peter