King poles usually come in paire, to hold up the front of a tarp (the back of the tarp is usually guy roped over the tent, using the front of the tent to make it's shape).
However, I think with a trailer tent you may need 3 king poles.
I think they usually have a "spike" (not sharpened) which pokes through eyelets in the tarp, where a guy rope is then attached to hold it all in place.
Someone must have a pic of a tarp set-up??? But from what you say, I think you've got the idea.
A shorter awning would probably be just as much faff as the larger one, but would be less pegs to bang in (I know from bitter experience that TT's have a LOT of pegging points

, very hard work in hard soil).
When I get a moment I will see what pics I can dig up.
4 Canvas tents (various sizes)
3 Plastic tents (various sizes)
& 1 Tin tent (yes, I'm a turn-coat, but it has a canvas awning)
My other passion;
My 1983 BMW 525e
France trip blog