It turns out the SA 4200 is supported by the PVR-150 IR Blaster firmware. It is codeset 41. However, the actual hardware does not support the SA 4200.

This is because the PVR-150 IR emitter is a visible red LED and not a true IR LED, and is not powerful enough to be "seen" by the SA 4200's IR receiver. (At least my 4200 did not see it - others have reported success).

So I dug out an old VCR remote, desoldered its IR LED, and replaced the tiny red LED with the one from the old remote, and whattya know, that did the trick.