The tray is hard to use, I had trouble starting out. I have only a few 7 cell NiMh pacs left now and its impossible to use the tray anymore with the config the cells are in.

A word about lipo "danger". Utube vids that show them exploding are generally the result of seriously overcharging at 10 times (or more) the proper voltage and even then, it takes some time before the lipo goes off. These are also usually not modern, current generation lipos - lipos for sale today are much safer than what was sold 5yrs ago. There are some legit instances of lipo probs, but the %'age is prob about the same as getting hit by lightning. People tend to be lazy, they don't educate themselves about them, then they don't secure the lipo in their RC properly or adequately, they have a wreck, the lipo shifts, pinion gear chews up the power leads, it shorts the lipo and the rc is burned to the ground. Thats the other common one I see.

You have to know a little about lipo, the safe and proper handling - you do not drop, throw or mash them in any way, they have a strict voltage range that they should never be outside of and you have to have the correct charging equip for lipo. Just today I saw a seriously damaged lipo on RC Groups where the owner had charged it using his radio's wall type NiMh charger and left it on trickle overnight, 2 serious mistakes. It was badly puffed/damaged. He was lucky he caught it before it burned his garage down. But was this the lipos fault? No, it was strictly the owner's fault like most lipo incidents are.

Lipo danger is overhyped.