Not positive on how to do it with a popup, but i'm sure google does! I'll be sure to come out with an alternate version shortly.
Edit, nevermind, it's just like regular pages. Here we go.
Code:
Actually, just search for this in the template change you made:
var winpops=window.open(popurl,"","width=,height=,scrollbars")
Change to:
var winpops=window.open(popurl,"","width=500,height=300,scrollbars")
And it should be fine.