Have you personally experienced a Lipo battery fail in such a spectacular way under normal RC conditions? Or do you just not like Lipo and want to scare people? Either way the end of your post was totally pointless, under no circumstances should/would anyone plug a lipo of any kind to a wall socket!
Personally I have never seen a Lipo fail under normal conditions, granted I have not been around them very long either tho. I have seen at least 2 NiMH cells go bang in a fairly major way under what I would call normal use (not BRCA Recommended tho), luckily there were no injuries.
Regarding saddle Lipo in a B4 I would do as Roger suggested and check the dimensions as can be found on
www.trakpower.com