Hi, I've sailed a lot with the iS122 these years and I am very happy with it: i'm waiting for the 121 now..
The board is superb with 7.5 range sails but I think it's even better with the 9!
But, since I see you also have a 114 slalom board (I guess about 70 width) I think you should really go for a iS 133.
iSonics have a really good range and it's reductive to sail it with only one sail: with the 133 you can go nicely with the 9.5 - 8.3 range and you can put 7.8 down sails on your 114 jp. Sell the hifly! :-)