Thanks for your input Ray, that's exactly the type of opinions I was looking for. I work more frequently with A32S types in which the normal MACs range from 25 to 32 approximately, and I guess that was one of the reasons I was in doubt, due to the apparent difference of the values in comparison.
I just did a single leg flight, fully loaded in single class configuration, and the loading was very similar to what you mentioned. 4 - 400 kgs, 3 - 650 kgs, 2 - 150 kgs, 1 - nil. The MACTOW was 21.8, exactly in the range you mentioned. Thanks once again, this type of info really is useful in helping to become more familiar with the a/c and preventing any unwanted surprises
Cheers