If you do happen to do your own, GTB 4 cell convert, be sure to retain the "gap pad" that is under the stock heatsink. That must be used and not be torn.
On a new ESC its fairly easy as it's not been through a good hot cycle yet, but after you've run them a few times, the material can be kind of tricky to deal with. Just go slow and lift it carefully.
The GTB 4 cell is quite a bit lighter then the standard GTB, and there are some minor profile revisions and value changes to better suite the usage.
Default profile starts out at lowest minimum drive as do all the profiles. The Drag Brake percentages go int 3% increments instead of the standard %5.
Also, the input plugs/switch are hard wired with no pins. The main goal of the GTB 4 cell was to offer a out of the box, race ready oval/12th scale BL ESC. Lower for the GTP bodies and oval chassis mounting locations.