Exactly, 6 would be to big for a one deck quiver, ++ too stiff. I found in one place, that 5,5 has effective edge of 1150mm, sounds small. Snowboard Dupraz D1 Mountain Workers 2009/2010 :: Snowboard and ski catalog SnowDB.com
4 years ago season it 309 nose 255 waist 297 tail width and 1150 eff. edge, and 2015 season has 310, 256, 298, nothing on eff. edge.