I've installed some infrastructure for the average speed SPECS and from what I remember, I think the cameras are paired, so if there were camera's A,B,C,D,E,F then you could get checked A>B, C>D, and E>F but not to B>C, D>E, but don't quote me on that.
I also appreciate this is zero help mind as you will have no idea which cameras are paired together.
You can put cruise on around 53-54mph, that way you deffo won't go over and you will be able to overtake those that try and manually hover at 50 on this inside lane without cruise (but just end up varying speed up and down). 55 or higher may be risky in some places which don't allow 10%.
I've found that putting cruise on at 50 will just end up in you having to cancel it, as you gradually catch up others in inside lane but don't have enough to be fast enough for outside lanes to outdo most overtakers, and you feel like you're just holding people up.
I prefer the limiter though, rather than cruise, just stick the limit on 54 and then forget about it.