2 x 26650 configuration

I'm looking for some 26650 batteries to use in my convoy L5 host, here is an other topic from me about this host and what to use: http://www.candlepowerforums.com/vb...-MT-G2-driver-with-2-cell-light-(26650-18650).

This topic is primarily about the batteries.

Some basic info:
2 cell in series.
Not yet sure about what led to use, there are a couple possibilities:
MT-G2, might drive it to 4A, not much higher then that.
XHP50, same as above, maybe 4A, not much higher.
XM-L2, probably also 4A.

There is not much room to fit 2 protected cells, I measured it at 137mm, so 68.5mm for a single battery. I might get rid of the spring on the driver board to increase it with 1mm.
So there isn't room for protected 26650, at least the ones I've found.
That brings me to my first question, how safe is it to use 2 un-protected cells in serie?
And second question, what kind of battery do I need, a high capacity or high discharge current battery?
Personally I want the highest possible run time.

Is this battery a good choice?
http://eu.nkon.nl/rechargeable/26650/keeppower-26650-5200-li-ion-battery-20a.html

Thanks.

Re: 2 x 16650 configuration

I know that there is a lot of info on CPF about this, but I just can't find it.

If anyone has a link or something that would be great!

Re: 2 x 16650 configuration

So I finally found some info on having multiple unprotected cells in series.

As long as both of them are bought, charged and used together it should be fine?
I will use a quality charger, I was thinking of the Xtar VP4.

That leaves just one question. But I think that it doesn't matter what kind of battery I use since the amp draw wouldn't be that high.