I'm pretty light on electrical so it's not a big surprise I have never heard of a Muldental Extension. The reason for using the 6 volt battery is so you have enough on board juice to operate your servos without allowing the battery to get low enough so you are getting brown outs in your RX. 4.8 volts work just fine if you have enough mah and check your voltage under load before every flight. A lot of people here are still using 4.8 but a small pack is 1400MAh. I use them but the smallest pack I have is about 2000. I also have a fast field charger so if for any reason {too many flights} my battery gets low I just top them up. The extensions I have connected to my RX are only 6 inch long so I don't need to be pulling leads out of my RX. Other then those two extensions you won't find any others in any of my planes. I just lengthen the servo wires so I don't require them. I know people use extensions and Ys without trouble all the time, I'm just not one of those people. A dirty lead is one of the main servo problems I have run into.