isonic '08 133 or 122 ? Help!!

[G]

need to buy the right board for Garda Lake slalom Masters Worlds in july....
..the course race will be down wind with start down to Ponale.

weight 80 kg.
sails NP rsr 9,0 - (maybe) 8,4 - 7,8
smaller board isonic 111
no experience with big slalom but race in Fw

thank you