In some lights, that would be fairly easy. In a D4v2 though, rather tricky. There’s basically no spare room inside, and the switch PCB is barely bigger than the switch itself.
Got a black and a gold D4V2 both XPL-HI 5D 4000k. I love them!
Nice. With those colours, they look like a pair of Duracell flashlights, except they aren’t crap!
I think I posted this somewhere else. It's just what you are compelled to try - if you have two colors.
It’s been done before. See Oshpark Projects - #525 by tterev3
But he uses a completely different driver design, with a different microcontroller. Plus I don’t think it would fit in a D4-sized package. Still something to dream about though. 
Finally got the magnets in after USPS in their infinite wisdom, shipped them all over the country instead of delivering them on Monday like they were supposed to.
The magnets are absolutely perfect! I'd say about 50-60% stronger than the one that came in my D4V2 magnetic tail cap. The original one would hold the light to a magnetic surface but if I bumped it, it would fall off. These new magnets hold pretty firm but not too firm- just right.
Here's the link again if anyone wants to get some.
Is it possible to disable turbo on the d4, basically disabling direct drive?
a true flashaholic would never think such a thought 
Is there firmware avail to support 219b?
The 219c one should be good enough
Afaik, every mode that is drawing more than 350mA of current is using direct drive, so by disabling turbo you won’t disable direct drive. If you want to fully disable turbo(level 150) I guess the only option is the muggle mode(6 clicks when the light is off to enable it, 6 clicks when the light is off to disable it). If you just want to use the light in regulated mode(no direct drive), you can configure the ramping mode ceiling, this won’t disable the turbo mode, but your highest level in ramping mode will be in the regulated range. While the light is on in a ramping mode click 4 times to enter the ramp config mode, then to configure ramp ceiling wait for the light to blink 2 times and rapidly flicker(buzz), then click 82 times, this will set the ceiling level to 69, which is probably the highest regulated level, actually it should be around 70 but due to the inaccuracy of calculations it is better to set 69 or even 68).
But for the exact level it is better to ask ToyKeeper, because there is also a possibility that steps scale in the stepped ramp is nonlinear and the value 70 was calculated from the fact that step 4 in the stepped ramp with default settings is the highest regulated mode.
It isn’t possible to disable it completely, but you can set the maximum to whatever level you want. The light will not ramp above that level. (You can still get to turbo using the double-click shortcut when the light is on.)
To disable turbo completely, you would need to flash different firmware.
Yes, the “d4v2-219” build is created specifically to reduce the maximum power level to make it safer on lights with more sensitive LEDs. I’m not sure if it is low enough for 219B though, since it is meant for 219C. So my recommendation would be to use the 219 firmware and use a lower-amp cell like a 35E or MJ1.
My apologies. I seem to have forgotten about the ways of the source, Master ToyKeeper.
Thanks! I’ll try that. On turbo, it was pulling 17A on 219b, on high, it would pull 8A. Swapping a 10A battery, turbo would draw 12A (a little concerned that more amperage is being drawn than what the cell is capable of doing).
Would cutting the PWM make the leds draw less amperage?
@trailhunter
Not quite sure what you are trying to achieve?
The D4V2 is a "pocket rocket" and if you want to use the high/turbo settings you should use a capable battery that can deliver the amps needed - your 10A cells will suffer greatly from this.
If you don't want it to be that bright adjust the ramp ceiling level maybe and just don't use turbo?
I know I am talking about a different light, but the FW3A with 219 firmware works very well with the 219B sw40 leds. I am not sure if the addition of one more led would break that or not.
17A / 4 LEDs = 4.25A per LED, they can survive that, but not by a large margin. Did they turn blue or anything? If not, change to the 219 firmware and call it a day, after all even if the FET isn’t throttled as much as the FW3A version it’s one more LED so the current will be split more.