You note it, it is formally inconsistence in my considerations. It is because I can't decide what solution to choose. But now (thanks to your help to) I have a idea: I sell my formula board and buy iSonic 150. It is good lighwind board, will be enough exciting with 9.5 slalom sail on winds about 10k, in contrast to formula (not forgetting about my heavy weight!). For heavier winds I'll buy 8.5-8.0 m slalom sail. If my health problem will end in future, I'll buy 11 m sail, but not as extremely race as Stealth.
On the other hand is sailing on Baltic Sea. In first concept I considered before, JP X-Cite was solution both for bay and lake, for the latter temporarily, up to time I will ready for bigger rigs on formula. Now I consider JP as bump&jump with quiver 6.4, 8.0, 9.5 sails.