Not on team but sail K96 as my high wind/wave board. I`m 95k and tend to agree with your husband that k86 would be a bit small for slogging in on. I dont think volume is far out but by time you have added weight of board/rig suit and harness you will be well over the flotation available.
I have a Tabou Rocket 64 (115litres) for on days when flotation security is needed. (its a similar board to S type but looser and less dedicated)
K96 on its day is incredible. (Best carving / gybing board I have sailed) but it will have unavoidable inherent weknesses when sailors over 85k use it.ie its just small.
Dont listen to lighter sailors saying you only need 5 litres reserve volume. A heabvier sailor carries heavier rig and needs proportionally more reserve volume to get same buoyancy. (Reserve volume is a nonesense) (Imagine a yacht with 5 litres reserve ??? It would be sunk! whereas a model yacht with 5 litres reserve would be fine)
Never sailed k106 but I think its a bit on big side for classic box.
(A k106 would carry upto 7metres ??? A 38cm fin in a classic box ???)
F2 Spice 106 ??? Smaller S type ? Or Rocket 64 ??