I had my eyes on one of the Hobbyking Zippy 4S 4200mAH LiFePo4 for quite a while, but every time I made decision to buy they were out of stock and over time I kept finding more and complaints over life and cell’s falling in the pack.
I noticed they no longer carry that cell pack now as 4S1P but they do have the 4S2P (which for Sota is same capacity more weight on paper) but maybe that helps the pack survive more as they discontinued the 4S1P.
I was considering going LiPo with a circuit because the 18650 I have for some torches, XHDATA SW receiver and other stuff all seem very reliable, when used with the appropriate charger of course. Need to find the right circuit to use with a KX3 though, and always nervous of some eBay regulator on an expensive radio!