OK, as I don't have any of the current 20 footers I can come from a position where I hve no buy into any class at present, so :

120kg - light but buildable without an autoclave ?
Width 10 foot / 3.1 M (the classic width = 1/2 length) ----- If you are worried about the hassle of rigging the thing at the other end; get up an hour earlier !!!!!

Mast hight 10.5 M
Mainsail 22sq M
No Jib
Kite 25; and why not make it mast head with a 2nd set of spreaders to hold the tip of the mast up....

No racks; they just qadd weight; When someone can build racks that are lighter than the difference in the 2 beams I'll buy them.