If it was me I would make sure that my 2 smallest sails fitted on the smallest board. Which would mean getting the I96.
There will be plenty of days when sailing your 7.8/133 when you wish the 7.8 was on a smaller board. Easier to drop board size than 2 rig another sail & possibly board etc.
I sail H111 F93 8.4/6.7/5.8 & are 85KG.