Hi Grob
a follow -up question along the same lines on catamaran sailors ideal 20 ft cat -it's design and features sailors would like to see -

Improvements from the standard benchmark Tornado design of a 20 ft cat may be a good place to start as the length and beam ratio seem close to ideal at 20 and 10 ft .

Here are mine -

Weight --as light as modern tech allows consistant with strength to race in surf and extreme conditions --
There are no standard stantlings for cat design loads -they vary with each designs various specifications .

Sail Area --the trend towards larger flat top mainsails continues ,-this is good . Some design sails per the rating measurement proceedures which rates this type of high aspect sail configuration faster ,which is correct ,-but it is a shame to add sail area where it is less effective to meet a rating rule .

Suggested a pure rating system for cats that uses only actual L B W SA measurements in a TEXEL type base power formula with a P handicap feature and same SIMILAR NUMBERS in P scale of relative time to distance traveled added to this basic pure design measurement number .--The only thing needed then would be top ranked T sailors of equal ability to spend a week or two switching boat types and racing each type to record comparative times, and we would all have a near perfect rating system .
sorry --off topic -

With the basics of L B W and SA established -that leaves specific features -
SAILS -jib no jib --preference -small self tacking jib
SPIN -higher aspect ratio -set further out on an extended pole -the longer luff dim .and higher angle is more efficient and creates more lift ,--via Aussie 18 type kites
A mid pole snuffer or snail type spin retriever --and would like to see a winch handle type devise used in the spin system to ease ware on hands and increase ease and speed of sets and spin take downs .
An internal type spin halyard system .

Would like a reef system for the mainsail -

Mast -CF LIGHTWEIGHT -in as areodynamic a section as possible --check out the current A Class cats --whew

Hull shape --canted hulls --deeper bow sections --eliptical top decks forward .

CROSSBEAM -radiused -higher off the water -in eliptical shape to avoid wave slap --the H-18 -designed in 77 is a good example -

BOARDS - canted -type --would not mind for and aft boards to help balance the spin --the forward boards angled to assist lift w spin --semi foiler type .

Rudders --larger -possibly a thru hull stern type design to help eliminate the cavitation problem .T foil shapes seem popular but have yet to sail with one .

TRAMP --more open areas for racing in seas --more storage areas and areas thought out for tools flares-extra marine radio -food water etc along with hardware leads and placement options .

Hardware --leads for control lines lead aft to stern trap crew positions -downhaul -rotator -etc
Forward location for spin blocks -center main sheet -
added cleats for temporary holding on spin sheet or others

built in electronic compass location on spin-pole

there are numerous other options -preferences and design aspects catsailors would like ,-sure I,ve not thought of numerous features and ideal options for a twenty footer - --Carl