If you go with any of the Life types in your glow powered LT-40 you need to understand Two things and that using the Life's is going to be a lot more labor intensive and no one ever mentions this part.
First Life's require balance charging with a capable Life charger system every time. Every time you charge there are now two umbilicals that are connected to the charger. Typically with most glow planes the batteries get buried underneath the nose area and are a royal pain in the butt to dig out. which you will have to do each charge or find some sort of balance plug adapter and extension.


Bottom line it is more work every time you go flying and I have had number of folks buy Life's thinking it the next greatest thing only to return to Nimh.


The pack I linked above in post #2 will serve you well with many long flights and remember Nimh is not old dead technology.


John