The sail on a Nonsuch is what we used to call (in early '70s) a high clewed blast reacher (heavy genoa). It is NOT a main. Trimming like a genoa works VERY well. Trimming like a main WILL work . . . but sailing performance will be very greatly diminished.
The sail on a 33 is the equivalent of a 150-160% genoa on an average 40 ft / 12 m mast head rigged cruising yacht from the '80s.
The boom weight certainly affects but was not planned as a method to control trim of the the sail, such as vanging. The wishbone "replaces", at the least, 10 ft / 3 m of hull aft of the clew & boom end to which "missing part of the boat" the genoa sheet would "normally" lead for trimming. You figure out how much that amount of hull and deck would weigh (let alone cost) and the comparatively minimal boom cost and weight is a GREAT trade off !
Ed Botterell (Olympic sailor, then owner of HOOD Canada, and builder of many offshore yacht and one design sails) designed the first Nonsuch sail with a small but useful input from Ted Hood. All the other lofts in the world, combined, have not built as many Nonsuch sails as Botts has ever since 1978.
The boom weight (the aluminum booms are less than 200 hundred pounds on a 33 or 36) is a function of what materials were available (and affordable) in the late '70s. The first boat built, NONSUCH, almost debuted with laminated teak booms a la Windsurfers and Freedom 40s of that vintage. THE FIRST aluminum booms were not "curved" but made up from quite a few welded sections . . . the first booms . . . welded sections ! photo - Nonsuch Photo Galleries photos at pbase.com
The weight of carbon fiber booms on the very small number of boats built post 1990 (many have been semi-customs) is less than an aluminum boom on an average 35 ft / 10 m cruising boat.
The foot of the sail "vangs" the sail.
"Choker" trim (similar to but not the same as an outhaul on a main) helps flatten the sail, closes the leech, and induces "vanging" of the sail.
Toppinglift always WELL EASED after sail is hoisted. Topping lift is for boom support and NEVER comes off when sailing a Nonsuch. It may be calm when you try taking it off but if the breeze comes up, even a bit, you'll never get it back on . . . safely. STAY WELL AWAY from the boom end when the sail is up. The sail on a 33 is the size of a main sail on many current 50 ft / 15 m cruising yachts. Would YOU try to go near, let alone hold onto, the aft end of one of those with the sail up?!?
Topping lift trim and adjustment in light air is very useful . . . IF you know what you are doing.
I'm 6'2" / 1.8 m and the booms and foot of the sail easily clear above my head on any Nonsuch model . . . 22 through the 40 . . . when I'm standing in the cockpit. I can't say that about many 40 ft / 12 m or larger sloops I've sailed and certainly not about smaller boats !
The most effective way to motor sail a Nonsuch upwind is to flatten the sail (halyard, then cunningham-if rigged, then lots of choker) and then over trim the sheet slightly (boom end just INSIDE a vertical line, relative to the horizon, up from the gunwale).
Most effective way to make down the boom end . . . when sail is down . . . is with a line tightened down hand hard to ONE quarter (not a "bridle" to both quarters) and then trim the sheet till it's hard. The well loaded and triangular configuration secures the boom end VERY well. If you utilize launches on a mooring . . . use the port quarter, which moves the booms off center to port. If you are on a dock . . . use the quarter and move the booms off center away from the side on which you dock.
Currently own 30C on Lake Ontario and 30C on Gulf of Maine plus an assortment of smaller sail boats and wood power launches.
Have also owned 26C, 33, and 30U Nonsuch models.
The Nonsuch "website" I created and manage . . . Nonsuch Photo Galleries's Photo Galleries at pbase.com
Have also owned and/or raced many kinds of sailboats from 10 ft / 3 m to 120 ft / 36 m.