Many different ways to do this but here is what I have found works for me. If you put a short piece of silicon tube stretched over the wire it gives the shrink tube something to grab for a better seal. Pics should explain.
This is a Shaman that was busted up so I rebuilt it and made my own cowl and permanently attached it to make the electronics enclosed. Gives a lot more room than a wood box under a cowling.
Mic