I'll have to double check but I do not believe there is a length restriction. Florida issues a concealed weapons permit which allows you to carry knives, guns, OC (even larger then 2oz), ect. Along with my Kimber I carry a CRKT My Tighe assisted open pocket knife.
790.225 Ballistic self-propelled knives; unlawful to manufacture, sell, or possess; forfeiture; penalty.--
(1) It is unlawful for any person to manufacture, display, sell, own, possess, or use a ballistic self-propelled knife which is a device that propels a knifelike blade as a projectile and which physically separates the blade from the device by means of a coil spring, elastic material, or compressed gas. A ballistic self-propelled knife is declared to be a dangerous or deadly weapon and a contraband item. It shall be subject to seizure and shall be disposed of as provided in s. 790.08(1) and (6).
(2) This section shall not apply to:
(a) Any device from which a knifelike blade opens, where such blade remains physically integrated with the device when open.
Florida · Summary: A "common pocketknife" is OK. All "concealed weapons" (knives included) require a license. · Max length: None apparent. · Relevant laws: Chapter 790
This is what i found on knives in florida.