someone said to me to port my primary plates the same size as my secondary plates so that all ports open at the same time ,do you guys think i need to do this to my 20b plates.

You'll hit the water jacket.

seen them done on a 13b and they did not get into the water jackets.

You cannot go down as far on the primaries as the secondaries without some tapering around the water jacket. You can make the ports open and close at the same time. Just remember that out is open and up is close. You don't really want to go down on the primaries anyway because there is no way to match the primary and secondary port runners. Now I can't give you the technical reason for it, but I can tell you from experience that there is no power increase in making them the exact same size and it can cause slightly lumpy idle.

i know you cant go down on the primaries but thanks for the info ,seeing that you dont make any extra hp with porting the primaries as large as the secondaries ,guess i would just leave it the same.