Bonechill Support - Stackable Or No?

SO.

I’m working on a variation of Ziggy’s Walking Blizzard multi-DoT Occultist, and a question occurs to me concerning the Bonechill Support gem.

Simplified, Bonechill reads: “Enemies chilled as a result of supported skill take 10-29% increased Cold damage over time. Enemies chilled as a result of supported skill take [X]% increased Cold Damage, where [X] is your Chill Effectiveness on that enemy.”

The skill also provides a whacking buttload of increased effect of Chill, which is nice, but my question is mostly procedural and kinda tricksy, hoping there’s some mechanics folks better’n me out there which can help.

Say I link Bonechill to Cold Snap, at level 20. Cold Snap, after Bonechill, has +50% Chill Effectiveness (for ease of calculation). This would mean Cold Snap(‘s Chilled Ground effect) increases enemy cold DoT taken by 29% + 10+(1.5x10%), or 15%, for a total of 44% increased cold DOT taken from Bonechill’s effects on Cold Snap.

Say I also link Bonechill to Arctic Breath, in the same build, and hit one target with both skills. Arctic Breath also has 29% + 15% Inc. Cold DOT from its own Bonechill, as the enemy is also standing in the Chilled Ground from Arctic Breath at the same time. We will assume for the moment that Cold Snap’s Chilling Ground takes precedence over Arctic breath’s in terms of actually Chilling enemies, due to Cold Snap having an innate ~19% Inc. effect of Chill.

I’m aware that only the highest-magnitude Chill effect applies at any given time, but as I understand all lesser Chills are still applied. They’re on the enemy, they simply have no effect on its movement speed while a greater magnitude Chill is slowing the critter instead. Given this, would both Bonechill Support gem’s effects apply and stack, for a total of 88% increased cold DOT taken by the enemy from Bonechill gems alone?

Would only one Bonechill’s “Cold Damage Increased by Chill Effect” mod apply, i.e. the greatest-magnitude one, while the basic “If you’re standing in the ice you take 10-29% increased Idiot Damage” apply?

Or is Bonechill applied as a named debuff to critters, a’la curses like Frostbite, and only the highest magnitude Bonechill gem applies such that a second Bonechill is a waste?

I’m aware that overstacking damage-taken modifiers reduces the value of any given such modifier, but in this case Bonechill adds a lot of damage-taken penalty to critters. Enough that I’m imagining it’s at least equivalent to a Hypothermia or a Controlled Destruction, even when stacked with itself once. Provided it does stack with itself. So…anyone have any idea if Bonechill’s effects stack from multiple source gems, or if it’s a strictly one-Bonechill-per-build thing?