RE: formula with freerace o race sail ?
To have "the earliest planing" perhaps the new Apollo with a 9.5 m2+
Free Race type sail would be the best combination, but the '05 Formula 159 and the '06 Formula 160 would be good choices as well, but they are not as free ride oriented as the Apollo.
Planing in 6-7 knots really takes the right combination of gear.
I've used Sailworks Retros and Severne Gators on the F-159/160/161 and they get going very early.
A Free Race sail is probably the best type of rig to get "the earliest planing" as they are a little lighter and less complicated and are easier to tune than the big Formula Race sails.
A 75% mast is definitely less expensive, but when you get into the longer, stiffer 490/520 cm or larger masts, the additional weight of the lower carbon content can sure be noticed.
For larger sails, I think the 90-100% carbon masts are really better due to the weight difference.
Hope this helps,