I fitted an XD dash to my XF a few years ago. I soldered all the joins, staggered them & covered them in heat shrink. Also immobilized the loom so the solder joins don't crack. Not long ago I converted it from straight gas to straight petrol & I crimped all the joins & terminals. The crimped joins are very strong when you use the non insulated terminals. To join two wire together such as a butt join I just cut the spade section off a non insulated terminal & use the crimp end of the terminal & stick the two wires in there & crimp it. If done properly it will never come apart.
