II do solder the 8G cause they barely fit and there maybe some loose strands but the crimp should be very tight and do a very similar things that the hydraulic crimps do in mashing all the strands together making no possibility for corrosion. However if I use 30 A and i know the wire is to big for a 15 but to small for a 30 and the crimp is partially questionable I do hit it with some solder... But also gotta remember flux makes things soooo easy... if you are smart you can get some really thin diameter solder and crimp it in with the wires and heat it up with a torch and its quick and easy.