Somewhere out there in webland I came across a blog of a french couple who built a larger (50+ feet) Wharram
and had a pair of unstayed junk rigged masts on it - one in each hull
. They were happy with it. I've lost
the link sorry. They also had hybrid electric
drives, which is how I came across them.
I think the problem with putting one unstayed mast
in the middle of a cat is there's not enough structure there for a decent bury, unless you beef up the whole area to the point where the weight gains become unacceptable. Maybe look at how those aerorig cats do it; there are a couple around. Windward performance especially in lighter airs is also, as noted above, reportedly an issue with junk rigs.
I stand to be corrected on this; there is elegance in simplicity, not to mention cost savings. Love to hear from anyone who's made it work.