I'm interested in getting another suji eventually, largely just for something different, but I don't slice large cuts of meat so I feel like 270+ lengths may not be useful to me. I mostly eat fish/chicken and I'm a home cook.
I have a 210mm Minamoto-Kanemasa suji in 2N carbon steel I largely use to trim and slice chicken breasts. It behaves well in that role, but I find it a little too flexible for vegetable tasks, though I have at times grabbed it to do small amounts of prep (an onion, a few apples, etc.). It is great for tomatoes but it isn't confidence inspiring on anything as hard as an onion because the tip wants to deflect.
I don't want to answer your questions with another question, but I must ask, do you like the 210mm sujihiki? Besides the flex of the Minamoto, is there anything else that detracts the appeal of it? (Edge retention, blade thickness, etc)?
The Konosuke has all the attributes I want for a sujihiki but they have a decent amount of flex in the blade. You may have to try a thicker sujihiki for less flex.
I may recommend a 240mm sujihiki. (if you're not deboning chickens. 240 would be too long for tasks like that). The length of a 240 will give you more blade, moving the cutting action more toward the heel and lessen tip use when slicing and chopping. This may help issues with the perceived blade flex. Although the gap from 210 to 240 is fairly small, the knife strokes will be different and may make the small tasks more manageable.
Let me know what you would change of your Minamoto. I'd be happy to help you search for a knife/steel you'll enjoy more.