Most people who are starting 12th scale are coming over from another class of racing, so will be experienced in cell building, but even so there are a few things to look out for.
There is pretty much a standard cell layout for an L4 which can be seen in the pictures below. Note the sides that positive and negative are on. Please excuse the soldering, these are the first cells I have ever built! (If you are at all unsure about building your own packs get someone else to do them. Bad soldering can damage the cells with dire consequences!)
Different people have different lengths of link wire going between the halves of the saddle pack. Some have a long link that can go over the centre shock. If you do this you have to make sure that it is not so high that it touches the bodyshell. Others have a short link that goes under the shock, like in the pictures above. In this case you have to make sure the link does not catch on the shock or the top plate of the pod.
If you fit Corally tubes as are used above (connectors of some sort are now compulsory, no direct soldering allowed) make sure they are high enough not to catch on the T-bar. Also make sure that when you fit the plugs they also do not catch on the T-bar. These things can cause very strange handling and are hard to diagnose, so eliminate them at the beginning.
