Heavy Air Mainsail Trim
I certainly agree with your last couple sentences but what you seem to be ignoring is the vang. Once the boom gets past the point where the mainsheet''s position of the traveller results in a predominantly downward force, the boomvang should be used to control twist. At that point you are ''vang sheeting'' which is very effective in blading out a sail. Going back and reading this string at least some of the posters have Hunters without backtays and so the option of increased backstay tension is not offered to them, but on boats with fractional rigs and masthead boats with flexible spars, backstay tension and mast bend are one of the most useful controls that you have in heavy air. On boats that have more primative rigs about all that you can do is to just tension outhaul, and halyards, drop your traveler and reef early.