Thanks for the suggestion to use my circular saw, but I want the most accurate cut I can make without a table saw and without having to make a guide. I am very careful using my radial arm saw, especially for ripping. As with any power tool, knowing how to use it safely (and doing so) is paramount. I am asking the community for best practices.
First, you need to rotate the carriage so the blade is 90 degrees to the arm.
Second, you need to unlock the bevel adjustment to set it at your desired angle and then relock it. Check it with a bevel gauge and verify it. The blade should be on the side of the table closest to you, not inside by the fence. The rear end of the motor will be higher than the front, where the blade is. This is so you don't trap the stock between the tilted blade and the fence.
Third, you need to understand which direction you MUST feed the stock into the blade. The sharp points of the teeth will be coming at the work, trying to lift it off the table. To easily prevent this, rotate the blade guard/cover around so the nose just touches the stock... barely. This will prevent "lift off"!
This is all done with the saw UNPLUGGED!
This also done with the arm elevated so the blade is not touching the table ....yet!
Once you are happy with all the new adjustments and they are all securely LOCKED, then plug the saw back in and turn it on. Be ready to shut it off if there are any weird sounds.
Now for the fun part. You MUST have a straight and flat workpiece!
The straight edge will ride along the fence as you feed the stock into the blade and you MUST keep it in contact with the fence the entire length of the cut. You MUST use a push stick to feed it the last 5" or 6" until it's completely cut.
Focus on the cutting progress and that the piece is always registered against the fence and you will do just fine.
This video is a pretty good one. Others are not as safe in my opinion:
Now, for the "scary" part ...dados!