Well, try as I might, I have yet to actually find a picture of Fallschirmjäger with the 6-mag MP40 pouch. In fact, in my book on Crete, despite many FJ being armed with MP40s, I have found only one pic of them actually wearing any mag pouches at all - in this case, the 3-mag ones (impossible to tell if it's blue or green).
So just how common were they??
You've got nothing to ein, zwei, drei, vier
I have seen a posed studio pic of an FJ wearing one and a hardshell holster - can't find it now tho.
Maybe they came in post-Crete?
Yes, they all have hard shell holsters. Maybe FJ just stuffed the mags in their pockets or something - perhaps pouches were considered too bulky to carry?
You've got nothing to ein, zwei, drei, vier
I seem to remember seeing one photo but I can't remember where and I hope I'm not imagining it. I think its safe to say they were pretty rare so it would be better to stick with triple pouches.
As to the chaps on crete without pouches perhaps they originally dropped with rifles and picked up the MP40s from the cansiters but didn't have the necessary pouches? The drop was a mess with heavy casualties so it would make sense to take the weapons that would give you maximum firepower rather than stick with what you had been issued.
Done a lot more searching and not found definitive evidence of any 6-mag pouches yet. Quite a few photos seem to show FJ wearing what looks like a slightly larger version of the leather map case on their right side. Many pics again with no mag pouches at all, some with 2x3 MP40, lots of K98 bandoliers (even at Eban Emael) and a few FG42 bandoliers.
You've got nothing to ein, zwei, drei, vier
Soldat, Volume Eight, has pics of FJ using 6 cell mag pouches. You'll also find quite a few pics of FJ wearing no mag pouches at all. The lower smock pockets are superb for carrying spare mags and stick grenades.
When we were a Kingdom it was run by a King
When we were an Empire it was run by an Empress
Now we're a country we're run by a..........
Here's another way of wearing mag pouches. 
From Martin Pöppel's book "Heaven and Hell" (his war diary). This is him preparing to take off for Crete.
(Excuse the quality of this pic - it was very small.)
You've got nothing to ein, zwei, drei, vier
Now that then begs the question who did use them. In the book Uniforms of the German army 1939-45 I have not seen any Heer using them. So if that rules out Heer and Falshcrimjager, it really only leaves Panzer and SS.
The 6-mag pouches were only used by FJ as far as I know, Pat... just not as common as I expected.
You've got nothing to ein, zwei, drei, vier
Soldat, Volume Eight, has pics of FJ using 6 cell mag pouches. You'll also find quite a few pics of FJ wearing no mag pouches at all. The lower smock pockets are superb for carrying spare mags and stick grenades.
Which campaign were those pics from? I spent about 2 hours looking through the Bundesarchiv photos for pics of FJ with six-cell pouches and also couldn't find a single one (but lots with them wearing no pouches)
I would also like to see some pics of the 6mag pouch in use as in all the various books i have i dont have a single pic showing them in actual use during WW2.
Could they be a fantasy item?
check out soldat vol 8 for info on the 6mag pouch and pics.
or if you have time, check the bundesarchive (60,000 + photos ) and you will come accross FJ wearing the 6mag pouch,
Freiheit ist nicht frei
Alle sieben Sekunden stirbt ein deutscher Soldat ,,,,,,,stalingrad massengrab
I have also found a photo of an NCO from around 1940 wearing 6 cell pouches.
Post it up, old chap!
You've got nothing to ein, zwei, drei, vier
old chap!
Old chap! 
sounds like your on the wrong side lol 
old chap!
Old chap!
Sofort Posten. SCHNELL!!!
Post it up, old chap!
Ah the distinct lack of a scanner is a bit of an issue. the book is Fallschrimjager Rgt 3, vol 1 (from storm battalion to regiment 1916/1941) by Klaus J Peters. Its on Pg 124. NCO wearing a 6 cell ammo pouch, map case and luger holster. His helmet is an M1938. I'll se if I can find a photo on tinternet.
The latter for me, Stu. From the lack of photographic evidence, it would seem that the 6-mag ones were very rare. But they did exist.
You've got nothing to ein, zwei, drei, vier
I have found two triple MP40 pouches to be more than adequate, I could probably just make do with one, but that would look untidy.
Cheers
Martin
"Mistakes in the initial deployment cannot be rectified" Helmuth von Moltke
Toys: AGM MP40, Cyma M1A1, TM M14/G43/SVT40, TM VSR/K98, SnS No. 4, ASG Sten, Ppsh.
Arnhem3,Gumrak,Campoleone
One pouch with a pistol is a classic look.
You've got nothing to ein, zwei, drei, vier