Script to add title screen before Quicktime movie

Okay, here’s what I’m after. I’ve written a simple script that adds a title screen before a Quicktime movie. Here it is:

tell application “Quicktime Player”
set the position of movie 1 to 0
select none
set the clipboard to the text returned of (display dialog “Enter text for title screen here:” default answer “”)
paste
end tell

This works just fine, but I hate the way the result looks. The text shows up small and inside a “frame” (don’t know what else to call it, it’s the same width as the video track of the original movie but has a much smaller height) way up at the top of the screen. I’d like it to be larger (maybe 24 pt instead of the default 12 pt) and vertically centered.

I’ve tried adding a line like this:

set the default font size of text frame 1 of track 1 to 36

This has the effect of increasing the text size, but not the dimensions of the “frame”, so that long text gets cut off.
I’ve also tried increasing the “frame” size with

set the dimensions of track 1 to the dimensions of track 2

This enlarges the “frame” all right, but distorts the text.

There’s something I’m missing here… I’m sure it’s right in front of me. Any help?