Tried a few ways over the years, i found if i mount both lights to 1 headband it tends to be heavier than the elastic can cope, so your forever pulling it up from over your eyes.
It's very very rare i wear 2 lights on my head.
The H600 and SC600 are THAT close in beam and light output i find that there is no real gain in using both at the same time.
The SC600 only throws slightly more than the H600 and the H600 only floods very very slightly more than the SC600 so you don't really get much of a gain in anything using both together.
The H600 is usually in my dog walking bag, so that's the one i use most the time.
The SC600 is in my bumbag.
This bag is usually with me when i'm out the house as it holds my phone, keys, wallet and a very very basic FAK.
I guess the yanks would call the SC600 my EDC light.
Sometimes i'll swap the lights around though.
I do prefer the SC600 beam slightly over the H600, the H600 is more useful being on the front of your head though i find.
If i know i'm going to be on a rough track or a path i don't know well then i'll take a second torch with me that i'll hold in my hand.
Mostly this is my Fenix TK35 as it's a fantastic beam and a great thrower and works very well with both the H600 and SC600.
The TM11 is a little heavier than the TK35 and a LOT brighter, but i do prefer the TK35 beam.
The TK70 is a monumentally great torch.
It's mega bright and the beam is the best i've yet come across, enough flood to be really useful and enough throw to downhill on a MTB comfortably at 50mph at night.
It's just a bit to big and heavy to carry for any length of time
So it's probably 80% of the time only the H600 or SC600
20% of the time either the SC600 or H600 and then supplemented by a hand held torch.