Hi. Almost any mast will bend if you tension the backstay. ALL masthead racing boats use this as a tool to control mainsail shape. Think of it like a bow (bow and arrow). The backstay tension is compressing the mast against the base. That load is translated into bend-like a bow. The amount of bend of course will vary with the characteristics of the mast section, but very few masts on boats like yours are that rigid. This is nothing new. Ideally if you have an adjustable backstay your rig tune should have the the mast base at the aftmost position, and at the partners it should be blocked somewhat forward of center. This will induce some prebend. This tuning should be based on the design of the mainsail-principally the luff curve.
In any case, you should start seeing measurable bend around 1500 lbs, and at 2000-3000 pounds I would expect 3-4". This is not a lot of bend, but if the main was designed with 4-5" of luff curve, that 3-4" of bend will take most of the depth out of the sail -exactly what you want when overpowered. As long as the sail designer is aware of the available mast bend, they can buiñd a sail which can be adjusted through the full range of shape/depth. This is why any sailmaker should be asking if you have a backstay adjuster, and ideally should come out and measure the bend. You can do this with a tape measure pulled up on the main halyard and secured at the gooseneck. If you note the distance between the tape and the back of the mast as you add backstay you will see it bend. If you feel you aren't getting enough bend, ease the lower shrouds a few turns on each side. Since the lowers are slightly aft of the chainplates for the uppers, if they are too tight they will restrict mast bend. DM me if you want a more in depth discussion
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