What method do you use to attach the bullet connectors? I've tried drilling the hole in the end out bigger, passing the wire thru and soldering it, then snipping off the excess and also turning the bullet open end up, filling with solder and while it's still liquid putting the wire end in and blowing it till it cools and solidifies - but that's near impossible to do on the car.
I agree, good earth connections are a must - many people don't realize the circuit won't work without a good earth......and you can't rely on getting a good connection just thru the mounting screw, you need bare metal.
I decided not to use bullet connectors and am using Deutsch DT series pins and sockets instead. they take up a lot less room, will take up to 2mm2 wire size and are rated for 13amp which is more than enough to handle anything running through the rear loom and headlight circuits.
the proper crimping tools for these are not cheap, and as i'm unlikely to make a great deal of use of it once i've done the loom, i'm soldering the connectors on; only done the ones on the rear loom so far, but they seem to take solder OK
once each connection is made it'll be covered in heathshrink, and then the bundle as whole will be wrapped in heatshrink as well - hopefully that'll help keep everything together, and for the headlight loom connections in the engine bay, it'll also keep the worst of the weather out.
this will make it a bit more difficult to disconnect the looms in the future, but i'm hoping not to have to do that too often..