What kind of light do you have? Skimming your thread, it said LEDs, but I just wasn't sure which.
If I had the PAR meter, I'd shoot for the 400s directly below the light 6" below the surface, and mid to low 100s on the sandbed. The numbers in between will be hard to control depending on optics, but I'd want to have high light areas up top and low light on the sand. I don't have any reason to think this way, except when you look at all the pictures of tanks across the Internet, regardless of the light type, this seems to be a common level of PAR throughout the tank.
An important thing to note... almost all LED lights seem "dim" to our eyes, but that's no indication of the actual brightness or PAR levels.
Nick Klase gave a great presentation on the details of LED lighting at MACNA 2014, but the long and short is that LED's don't produce green very well. Unfortunately, one of the colors that our eyes use the most to determine if a light source is "bright" or not is green. I think this is one of the reason that so many people were dissatisfied with early LED lights. In addition to not dispersing light as well as MH or T5s, LEDs look inherently dim because of the way they produce green light. As a result, I think many early adopters tried to increase the intensity of the LEDs to match what their old T5s or MH looked like. This ended up being way too much light because our eyes are so biased toward calling green-rich colors "bright", and green deficient colors "dim".
Long story short, you're going about it exactly the right way, with a PAR meter. It's really difficult, especially with LEDs, to tell how much light is too much.
