Jstraw:
I understand your question. I was less than enthusiastic about the RH flasher for the same reason. However, it is what it is which is what a few folks have tried to tell you and you've already bought it. Oh, well.
I didn't but one. What I did is what you are trying to do, I think. I experimented with a couple of different small bulbs, like a "night light" thing, and I have placed one near and bounced off the white ceiling of my darkroom. Attach this $4 item to an old Time-o-lite timer that was just sitting in a drawer, and viola', a flasher. Works fine.
But, each neg is different, and so I still make a test strip for each print. It just gets down to that. Yes, just exposing the paper to a fixed point is the same time, but you might not want or need that exact amount for this image this time. So, making a test strip if the flasher was attached to the enlarger neg stage wouldn't be any different.
Mounting the flasher on a swing arm next to the enlarger sounds like a good idea. But, I bet you still end up making test strips. Or, maybe not. I could be wrong ... :rolleyes: