I do not want to comment on safety, but I have consumed 3500 per day on several days without issue. 2500 is my minimum. If I get less, I will get weaker the next day. 3000 is perfect for me to thrive with basic exercise, which is all I am up to yet. I plan to keep pushing the limits of this, so I am trying to get at least 3000 per day spread out as evenly as I can, but if I am going to work out heavy, I will go for 3500 or more. I do notice that higher calorie intake kill of most of any muscle pain after the workout. If I have any soreness, I just drink more Huel and it passes pretty quickly.
I think the biggest danger is not getting enough good calories. If all you put in is good, the minimum is probably ok, but interesting things happen with sustained higher calories, in my experience thus far. I think so many people ar focused on minimum and maximum, but I say listen to what your body tells you. If you lack a little energy and muscle pump, that would be signs of not enough. If you have surplus energy and cannot expend it, you have had too much. Once you start listening carefully, it will tell you what it needs. Going all Huel and water, you will hear what your body is telling you much clearer.