Hi Ken , thanks for the post. The only experience I have from wide boards is with a jp slalom 82cm . Planed very early and really fast but felt like I was in a rocket. Too fast compared to wind strength and always felt that the board would fly over water. I'm 72kg. I find narrower boards more comfortable and I also prefer the easy handling of my 7.0 twin cam , I had a 8.2 twin cam and sold it , it felt too big and not much difference in early planning. Where I sail most of the time the wind never gets over 12 knots. There are RS:X with 9.5 sails and lots of guys with formulas and wide slalom boards with sails >9. I really don't see much difference in early planning compared to them to go to such big gear and when the wind drops no one planes but still the RS:X go faster with dagger down while we are stuck on water. Check this out.
Really light wind no white caps and when not planning still going really fast hooked in and front straps. Maybe the bat wings do the work providing a wide tail compared to overall width of the board. What about the bat wings on the phantom 295? Has the same tail width as 80cm wide boards.
No one has such boards here so no way I can test one.