I agree that, if you are over 20' you may not have a capacity plate...which I see as a good thing. If you have a capacity plate, you are required to comply with it.
I had a closed bow low freeboard ski boat from the 90s and its capacity was 6 as it is one the early Malibu Skiers but I don't remember the weight capacity. Both of those boats were more than safe with 6, in my opinion.
My advise, load it as long as you feel safe. It may not be a bad idea to let everyone know that you will be heavily loaded and ask that they not all stand in the same corner...we almost lost that Malibu with 12 of us (yes, 12) when everyone kept piling in the same corner! No one else noticed that we were within 1/4" of taking on water so I jumped out and and yelled at which point a few others caught on and more foreword.