Well, the LED lights I bought from Dollarama are working pretty well. They are those circular ones with the adhesive thing on the back, has three 'white' LEDs in it, takes three AAA batteries, press the lense to turn on/off............ you get the drill.
At first I tried a few things out. My workbench is about 6ft away and has a flouescent lamp on it. Because I've been swamped with gun work since before Xmas, it's mostly on. I tried various lighting situations, LED lights on top of the diffuser pointing down only (dark elsewhere), overhead light bulb (think it's a 100W bulb) on with LEDs, LEDs off with overheard light on, bench lamp on with all others, bench lamp only one was useless, the Chrony was doing the funky chicken.
My MK23 sat all the time between 210fps and 220fps, my MP5SD ranged (literally knocked off a few locaps of 0.20g) from 383fps at an EXTREME low, once, to 408fps at an extreme high once. Everything else out of it stayed within 10fps-ish , centering around 393-403 range, lots of 399-400fps readings. My other MP5, which I chronied after downgrading to be about 320-330 range, next day 300-305fps range, sits at 310-320 range, mostly in the 320fps area. My M24 sits at around 471-487fps range. So, this is tonight anyways, under lots of different lighting conditions. And much of this testing was done after I put velcro on the backs of my two LED lights and stuck them to the UNDERSIDE of each diffuser right above the sensors. So it doesn't seem to matter if it's LED on diffuser, LED with no diffuser (both cases lights on or off).
So far, the only thing mentioned that I hadn't thought about was what McGuyver said, about the voltage variances that change over the course of the day. Light is light, but I didn't know these sensors were sensitive enough that it could tell the difference between a couple of volts of electricity. Actually makes pretty damned good sense though, will report back over the next while and see if my cheapo LED lightsource fixes the problems I've been having.