There you are: Flash regex for the ones that need it

If you are talking about the hack you have to ask Mas Mind, if you are talking about the BB code I posted, then yes you can set up a fixed width and height, the problem is that it will be fixed so they can't have anything smaller either.
you can do this simply by setting it up on the code replacement.
It would go like this:

vB Code tag: swf

vB Code replacement:

<embed src={option} width=200 height=100 type=application/x-shockwave-flash></embed>

*NOTE that the width and height is the one that will be used on all flash movies, not only sigs!

vB Code example:

[swf="http://yoursite.com/yourmovie.swf"][/swf]

Use parameter: YES

This should work fine!