Used the 13/7 converter, which is the twist type, and it worked (photos attached). The twist is not a full turn but was secure, and my light board worked, and the trailer light came on the display. It is raining so didn't do multiple tests, but noticed that the trailer light needed to be manually turned off, so will test that out when the sun comes back. This adaptor was from Halfords, but can get them from most reputable online shops.