If I understand how the drop lever works, then actualy while it puts little compressive force on the boom, it puts a lot of bending. The sail is secured fore or aft of the car the mainsheet block secures to, so the bending is produced by the offset between the two multiplied by the tension (acting perpendicular) So if the car is way in toward the mast (traveller centered?) and the main sheeted hard, then this would be the worst, and not unusual scenario. But when you are travelled out, the car would be typically further back and more directly under the sail securing point, but typically without spin you dont sheet hard then...
The irony is that the old deep rectangular section is good in bending (up/down), but could buckle the weak (narrow) way in compression from the crazy mainsheet angle typical on Nacra Squares with traveller centered. The round Prindle is light and symetrical so it is a good "column" for its weight for longitudinal loading, but not for bending in one plane.
The Duhh trick that the "A" cats use is to load the mainsheet directly to the sail "around" the boom with a ring. The boom only pulls the ring in and out (outhaul) and so can be set up for pure compressive loads, and no nasty bending.
I guess you could do something similar, but you may have to have an inhaul too, when you travel out, to control your foot tension (or lack of it). The benefit would be that you could keep a pure compressive load and a minimum section to the boom. We could really geeek out on this.
The last time I tried to race I got in irons buggering around with the mast rotator, and lost say 10 boat lengths. How often does mast rotation gain you ten boat lengths, even cumulatively? How much a 10 oz lighter boom? Do it for the gee wiz factor. I have two extra Rectangular booms if you want one. How about sawing circular holes out of the sides to save weight? You could saw a lot of big ones out at the mast and less toward the mainsheet ( drop lever) anchor point. Or you could taper the bottom wall in and tig weld it back. Look real trick.