I currently leave a programming adapter, consisting of a six female pin stirp connector, within the heatshrink. The male counterpart can reach that through 6 pinpricks in the heatshrink. This allows reprogramming any time that is needed (e.g. in case you want to use the ESC on a differnt motor number or newer firmware becomes available).
Also I currently stabilize the wiring with hot melt glue. Had one bad experience with a TowerPro 18A v2008 which worked fine for several flights, and then suddenly failed (luckilly still on the ground). I found that the wire connecting the resistor network to the new port had shifted slightly and was now shorting out against the next processor pin. Easilly fixed but not good if that would have happened in flight.
My standard for the 6 pin connector follows that of the 6 pin mini-ISP, except that that has a 3x 2 bulkier layout. Mine takes up less space within the heatshrink. Pin 1 is the pin at the power input side of the ESC: 1) SCK, 2) RST, 3) MISO, 4) 5V, 5) MOSI, 6) GND. The 5V isn't really needed, but it's easier to stick to a standard then to do different things all the time.
TowerPro 50A conversion with programming adapter retained within heatshrink and wiring stabilised with hot melt glue. Same adapter easilly fits with TP 18A / 25A / 30A (with or) without BEC.
6 pin pricks give access to the programming adapter.
Male pins just push through the heatshrink into the adapter.
Male pins wired up: 1) SCK, 2) RST, 3) MISO, 4) 5V, 5) MOSI, 6) GND (brown), with pin 1 always at the power input side of the ESC.
The big advantage of this type of programming adapter is that ESCs can easilly be reporgrammed to new motor numbers or newer firmware as needed without having to remove the heathrink.
The advantages of using the hot melt glue (or epoxy) to stabilize the wiring are of course self-evident.