Well there are one of 2 things probably happening here...
1) Just because the drop-in coil for a Brand A fits and works properly in Brand B's tank it doesn't necessarily mean that Brand A's RBA will fit or work in Brand B's tank. It might fit into the tank but it might not seal either at the chimney or at the base properly. Therefore leaking.
2) If #1 is not the issue, then your wicking is no good for that RBA or RTA. You have to play with it. Unless the RBA/RTA is defective, leaking is usually no doubt a wick problem. Usually not enough cotton or the cotton is not in the right place(s).
I wish I could help you figure it out but I have never actually used that RBA. I actually have it, but never used it.
If you post pictures of your current build from the side at the wick holes and from the top, maybe we can help you better.