I do this all of the time.

It is a very fiddly job to get it working correctly.

I will only do it if the client is using Okidata DOT Matrix or something equivalent.

You definitely want to use a font that is built into the printer.

Speed is not a problem unless you try to print special characters or graphic images (in other words keep it to plain text).

I would never do it if I had to get one specification to work on two totally different DOT Matrix printers.