A very kind soul mailed me this programming manual last week and I have finished scanning in the entire thing. This manual has very extensive documentation about how to program the newer Sony laserdisc players such as the LDP-1450, including verbose information about how the text overlay works (which is what I've been working on lately). I am pleased to say that most (all? hehe) of my conclusions were correct.
You can grab the manual (for a limited time) from here: