Thanks for quick reply !
My IS 137 is brand new (bought yesterday), want to use mainly rs:slalom 9.2 m2. for light wind (3+ /4 Brf). I have FU 122 (2009) and I think it's not enough wide and volume behind, in heavy chop (4-5 Bft. on lake, like today, wind goes on and off) sometimes have spinout or loose some control. But when wind drops more floating than surfing, because 98 kgs.
Maybe FU 131 is close to IS 137 I know but IS is more light wind and FU is more medium wind for me. The rs:slalom 7.8 m2. off course is the overlap in sails. If FU 131 (2013 or 2014) is good suitable for 5 Bft. or even some more (can use rs:slalom 6.7 m2. on it ??) than that's a good option for me (more control in chop and less floating when wind drops).
I don't think IS 110 is better option for me, maybe IS 117 but that's to close to IS 137 (width 80 vs 85) ? Hope I can use my IS 137 soon, must be a great board !
Maybe I will like IS so much that I change my mind ...