extending some db tables

hi,

the main reason, why I ask, is that I am conserd how performance might change

I'm going to use punBB in my uni for systematic feedback about the subjects they learn:
actually each subject will be equivalent to topic, but what I want to have is :

main_text_about_subject
some_fields_for_some_metadata
+
text_about_lecturer_student_has
vote_about_is_teaching_interesting
vote_about_usefulness_of_subject

may_be_students_mark

now I think to add theese felds to `posts` table, and some vote_stats to `topics`.
I guess this is more performace friendly, but things can get complicated if db scheme changes -- just tell me, if there are no such plans .
but then `posts` table will more often used by SELECTs, as there would be options to review just votes or just feedback_on_lecturers...

other way would be to put up new (parralel) tables for additional info. But this would mean more code (duplicating data writes and reads, and so on..)

any comments are wellcome