@Haggar - I'm just under 100kg and primarily use an EVOIII 7.8 and 7.0. Where I sail the winds can very gusty and have large holes/long lulls so I prefer a little more volume. It also helps when I want to do the slalom races. Also, my other boards are a CarbonArt 62 slalom (about 100L) and an F2 Hornet 155L, so the 121 fills the gap better.
Along those lines, I have seen that that 2013 Futura 121L is a V bottom (so is teh 131) whereas the other sizes are V to double concave. Any input on this? If the V to double concave bottom is quite a bit nicer, that could be enough to talk me into the 111L size...