mmm 2200kv combo ok to run on 2s and 3s
 

mmm 2200kv combo ok to run on 2s and 3s is it ok to run around on 2s and 3s lipos sometimes or will it damage motor or esc? just sometimes my nephew come and wants to have a go so i just run 1 batterie pack so its not so fast will this be ok? i have 2x5000mh2s1p lipos at 20c and 2x5000mh 3s1p lipos at 20c when i bash and race i use them in series to make 4s/5s and 6s most of the time it runs on 4s and 5s

It's fine. Just don't gear up to compensate for lack of top speed. Also, the BEC will work better on 3s than 2s, so I'd go no lower than 3s personally.

my gearing is 20/65 is that ok ? so better 3s not 2s?

I assume that gearing is stock? If so, should be fine, just not very fast. Just watch temps on the ESC, motor, and battery for a couple runs and make changes as needed. And yes, 3s would be better than 2s for the BEC.

I personally tried 2S, and it worked flawlessly, the start got even smoother. overall you'll get a very gentleman-behaving toy.

Just on this, the Flux has the MMM speedy set up to run 2 packs in series, and the manual says to run two "identical" packs (which I can see you don't want a 5000mah and a 1000 mah pack)

But could I run it as a 3s pack on one side and a 2s pack on the other, say both 5000mah 25C to get 5s?

Again they should be the same cells and really age/num of cycles to avoid one pack discharging more than the other.

I also run the MMM/CC 2200 on 2s for my son (6) - simple matter of swapping a parallel to series adapater to get 4s for me...

Works well.

I run my Savage Flux on 6s 2x 3s 5000mAh packs.

Ive been thinking about running it in parallel as 3s 10000mAh with the same two packs.... is there any harness i can rig up to achive this?

or cause the flux comes with a series y harness direct from the esc so would i have to change that to a single deans connector from the ESC and make two seperate harnesses for running parallel and series?

Yes you can make a parallel harness like on this page (second part, "Use 2 parallel-connected battery packs") http://www.scriptasylum.com/rc_speed/_lipo.html.
I have done the same thing as that (6s1p 4900mah and 3s2p 9800mah) in my truggy with a 1515 1y 2200kv and it works well.
With the 2 plugs coming out of your esc, make one side the same as in the diagram, and for the other side use a plug with a bridge wire (just joins the two plug terminals), so it completes the circuit. You could make it so there's only one plug from the esc, but then you'll need to make a series adapter for when you want to run them is series, so it depends what you want.
Best to charge and balance them together in series even when running in parallel.