XRAY - Model racing cars

normally GP 3300 and Vtec 3700 cells will fit ( at least im my car I had no problems with those cells ) : I don't know if the "improved" Vtec cell's have a slightly different size, so can't tell you.

You will have to file a little bit off the bulk head near where the batteries sit. If you don't the front belt gets tighter every time you put the battery in. You may also need to put some small shims under the battery holder post to raise the battery holder or you can file the chassis. The shims are the easiest but filling the chassis will have a lower CG.