Really nice work!

The Model 4p must have had a better disk controller and software than my Model 1. The Model 1 used a Western Digital 1771 controller that required a pause between writing a disk command and reading the status. A few NOPs would do, but early versions of TRSDOS missed the pause out, causing frequent crashes.

I never did movies on it, but in 1980 managed to get it to record a few seconds of recognisable speech using the I/O line in the cassette port. Filled the massive 48k memory in no time.