mtgriff.. I also have a Scientific Atlanta 8300HD DVR and have a Universal Electronics Atlas OCAP 5 remote. I have been experimenting with the macros and found that after you press FF four times, insert a "0" (or any character), and within a couple of seconds insert your "play". I've found this effective, but you have to work with the timing of the "0" and "play" to get it just right.
The only way it's predictable, is that it's not predictable.