RE: @ Remi, Code Red R2 9.0 and 8.3
We don't recommend the skinny mast as the first option for the Code Red II. We found that the sail perform better all round with our Severne Red line masts and 370, 400 Blue line masts (for the smaller sizes)
We have a cam conversion package for those that still like to use the Code Red II sails with skinny masts, from 6.7 and down to 4.6. Speed sailors like the use of skinny mast for less drag.
For your Isonis 133 we would recommend the Code Red II 9.0. This sail is just flying - you wont be disappointed. Use the 490 Severne Red line with 30 cm tip extension, as Remi pointed out.
You can upgrade to the Code Red II 7.7 or keep your current Code Red 7.7, which you like so much. The new one has better low end.