So, I have the stock 380 connected to my SCT and it's great. The SCT barely gets warm and the motor is pretty warm (so need a fan). Anyway, for those of you interested you do the following:
1. Start with stock motor
2. Press new Castle bullets onto the end (so the stock male connector goes into the back of the Castle connector where the wires usually go).
3. Solder the pins together
4. Cover with shrink wrap
And your done. This was incredibly easy and didn't require cutting off the old connectors. I don't intend to go back to a stock ESC so the connectors are on there for good.
One issue I found is that the connectors are extremely tight fitting together. The connectors on the SCT are 4mm and that's what I got, but they were so tight putting them together that I don't know if I'll be able to pull them apart without pliers. Is this pretty common for brand new Castle bullets? I did check and there was no solder in between the cuts on the male end (I've been soldering for years).