With the SM versions like the 3SM and the 1SM you can use 2xRCR123's or 4xRCR123's with the extension tube. BUT I'm pretty sure only AW brand RCR123's are recommended for this because they are strong enough for the job.
I too am looking at protected cells. I did a run time burn test on my SF 6P tonight. In doing so I cooked a battery. I had ultrafire's in it and they only ran for 40 minutes until dim on my LED Q5.
Is that right!?!?
So I guess it would be a great idea for me to look for protected cells.
I started looking tonight....I found some from Spiderfire on Ebay - 3.7v 1000 mAh