Pfaffi and Mark are correct.
If you still want to do the formula races, you would be ill advised to get the Isonic.
Sorry, I thought you mostly did free sailing, not formula racing.
If you want to do the formula races (even local amateur ones) get the right tool for
That would be the F-162.
You are a competitive guy, so you need a competitive board or you'll be very frustrated when the fleet takes off for the upwind mark and you loose them by 5 degrees to weather. You can't make that up with better transtions at the marks or better tactics.
If the formula racing isn't that important, the Isonic 155, with a 9.5-10 m2 rig will get you going and be alot more fun IMHO.
Hope this helps,