Case For Rotobrush & Mask Keyframe Question

Question

Hi,
Just wanted to make sure the below sample is a case for Rotobrush.  Obviously I've never used it before, however I'd like to maintain the color, (excuse the crappy mask), I've created in the water in the first shot, throughout the sequence of cuts.  When the woman moves across the aquarium, I'll need to rotoscope her correct?  Any tips?  I will however be reading the manual!
http://vimeo.com/39579490
And the mask question - I should know this but for some reason, (in another comp), my mask changed shape over thime.  It was the same tank you see above, but it was a dolly shot and the tank didn't change shape!  You'll laugh but I ended up resetting the mask points in 291 frames, and it still didn't work as the variations in mask shapes created a flicker after applying color correction, levels etc.
Shouldn't I be able to go to the end of the comp.  Draw the mask shape I want, keyframe Mask Shape; then go to the beginning of the comp - set the position of the mask and keyframe again.  Please tell me where I'm going wrong!
And; is there a way to keyframe a "transform" of the mask shape during time?  Essentially changing the size and shape of the mask, I was only able to do this frame-by-frame.
As always, much gratitude for everyone's guidance, patience and knowledge!
Best,
Jesse

Answer 1

I actually wasn't using auto-trace, I drew the shapes with bezier points as one would in PS.  Not sure what you mean by vertices?  Didn't move the layer.  My apologies for not painting a better picture.  I'd like to post a screen shot, but don't see the camera icon!  How do I do that, is it possible without the hassle of using flikr or photobucket?
Ok, not quite sure if you answered my question, (and yeah, my 291 frame marathon freaked me out a little.).  How do I maintain the shape of a mask from beginning to end of a comp?  (there will be variations as it comes into frame etc., I think I can handle that), but why wouldn't the mask hold shape when I keyframed beginning and end?
Now, with the above referenced Vimeo clip, the shot where the artist crosses the aquarium - won't that require multiple mattes on multiple solids, or layers as there are a bunch of spaces where we see the aquarium?  AE will not allow more than one mask on a layer correct?  Unlike PS!!  Or am I wrong about that?
Would I be linking the solid with the matte(s) to a null object and then tracking that?
Many thanks again for your time - I hope my questions aren't too convoluted!
Jesse