Terry,

The only purpose of that center bar was to prevent rotation of the fore and aft cross beams. Later boats (all Nacras to this day) have a large bolt that goes from the center of the beam (at each end) and threads into a brass plate in the hull.

I've heard of 5.2s successfully removing the bar and installing small stainless screws successfully - but I never did modify mine in this way. I just got used to the bar (and kind of missed it when I upgraded to my 6.0).