The F-18 rules as accepted --
http://f18-international.org/rmeasurem.htm Several pages of defined rules -
The main differences from F-20 are -
1- the existing condition of several different existing 20s -some built to EU F-20 rule but most popular widely accepted 20 in the US is the Inter 20 US version that is 30 LBS lighter with a larger sq top mainsail at 210 sq ft inc C F mast.-The proposed F-20 rule uses the US version Inter 20 model as guideline for basic class specifications and encourages all others to modify up to that maximum specification in matching length beam weight and sail area .
2--Due to varied existing 20s w C F masts -comptips- and various rigging etc -masts and sails are only limited to a closely matching 32 ft length with spin bale a min 41 inches below mast tip --limiting spin -mast -and matching pattern sq ft main sail that must be within the I-20 model and match or be within sail shape with same or smaller top .
3- crew weight has a min 320 LB with equal added weight allowed for lighter crews to compete ,-no upper weight category is used for added spin area as per F-18
A dispensation rule is in effect as per early F-18 allowing older unchanged existing 20s exempltion to use existing configurations and spin size ---example -the N A 6/0 with NE spin --proven in competition to be close , -may be used -but once modified in any form must then comply with all aspects of F-20 inc spin size of 270 sq ft .
4 -limits on sail material or hull materials --there is a min. boat weight of 385 LBS -which effectively limits the use of materials --epoxy is commonly used for repairs during distance racing --but prohibited in F-18 .
Reef systems are allowed in F-20 .
Other numerous lesser rule limitations are defined in F-18 -the intent clause of F-20 states standard practises and configurations ,-meaning any unusual or different feature not currently used by existing 20s is not allowed ,---all teams entering a F-20 event would be required to provide full discloser of F-20 boat type and all modifications from the base model prior to the event . Anything not expressly approved as a standard practise or configuration is prohibited .
The class intent is clear --to race 20s on a fair equal basis based on principles of sportmanship in accord with event and ISAF rules of fair sailing .