Centering movieclips

Yet another center movieclip thread . . . I know you love it.
I did a few searches trying to find an answer to my issue, . . . i get close to the answer but it isn’t quite my same problem, so let me run this by you.

My project is making a webpage that has flash games on it.

I downloaded 10 flash games from the net, (.swf only ) and have them in a folder. On my stage, main timeline, I loaded a movieclip container, . . this is your basic load MC set up . . . Anyhow, with thumbnail images of the individual games set as buttons, I am loading in the games from the folder into my clip container. . . this is working like a charm, but I have 1 issue, the game clips are not all the same size so they wind up outside the target area. . .

I don’t want to resize the games, but I do want to at least center them on the stage.
Main roadbloack:
I don’t have the .fla so I can’t get into the flash file to target co ordinates. Not really sure if that will do the trick anyway.
I can’t seem to find out how to alter the registration points of each swf as this could be an option as well. . so I feel like I am screwed . . .
anyone have any ideas?
There is no AS of value anywhere other than the

on (release) {
loadMovieNum(“whatever.swf”, 1);

that I have on the buttons.
Thanks in advance