Matching up wooden post and post support/shoes

[stevej]

Hi, Im putting together some plans for a gazebo. The main posts will sit in metal post supports, however I'm wondering, if I have 75mm*75mm posts, do I need 75*75 post supports, or 80*80, ie are 75*75 supports usually intended to hold 75*75 posts, or do I need to buy 80*80 (next size) to make sure they fit in. Thanks