Trouble Going From PI into Vegas

Is there a tutorial someone can point me to so that
I can use ParticleIllusion with Sony Vegas 6.0?

Here's what I'm doing:
I'm importing a 720 x 480 10-second clip into PI
as a background, adding my effects (in this case, snow),
then removing the background and rendering only the snow as
a TGA with alpha channel.

In Vegas, I am importing this TGA file as an image sequence and placing it above the desired footage on the timeline--and now it is snowing on my desired footage. Here are the problems:

1) the TGA file sequence has a size of 598x480x32, even though the project settings in PI were set to 720x480. Is this normal?


2) For whatever reason, the snow effect is at least twice as fast as it was in PI. In other words, after rendering it in PI, it is now snowing twice as fast as intended, plus what looked like snow in PI, now looks like square snowflakes;

Any ideas what I'm doing wrong?