which way to render
 

Hello all
Ive been doing a piece of videoing with my daughter, where she plays both people I masked the second her in,the problem is shes looking through a mirror when the other her appears,and although i didn't move the camera or zoom, the bottom of the mirror is in the shot so i cut it out to crop it,rendered it, and then replaced it in the sequence but now its like a 4:3 look (no black top and bottom)which makes the effect look worse what am i doing wrong,and one other thing i wanted to know was i have hd 110 and a sony hc3 which i use for videoing my daughter when shes in shows,i was wondering if anyone could help me by letting me how they would render it,as the hc3 is 1080 and the jvc is 720 would it be possible to put the sony into 720 or ive noticed on the jvc that if you change native it has a 1080 option on it, as you can see im a bit confused i hope ive explained it ok,as any help will be greatly appreciated
thank you Tom

Hi Tom.

Which editing software are you using?

So sorry
Sony Vegas 9,i knew id forgotten something.

Sorry, Tom. I'm not familiar with Vegas. Maybe try specifically posting over on DV Info's Vegas forum for a faster answer to your questions.