Why bother?

That is more complicated that it needs to be.


Look at that picture you posted from my battery pack.

There was already a hole in the back for something, at the junction I believe...

But just use a small dremel sanding drum at the edge of the back, to create two semi-circles.

Do it so that when you put the bottom cover on, you end up with a whole circle.

Then just feed the wire through the circle BEFORE you put the bottom on.

Simple, and there is NO cutting of the Tamiya connectors involved.