FCPX Triptych / Project Settings

Pardon my ignorance... but any help would be gold right about now.

I'm working on a video to be shown on three projectors. Original project settings were 16:9, but the dimensions have been revised to 4:3 because of the available projectors and 1800 x 600 pixels (if we are creating triptychs within one timeline) or 800 x 600 if we are creating three separate films to be projected simultaneously.

I am creating triptychs (so going 1800 x 600) but when I create triptychs in the new 1800 x 600 settings, I get three squares. Isn't this in conflict with the 4:3 ratio? Shouldn't each triptych appear horizontal?

Apologies again if I am confusing something obvious, but as I am starting again from scratch (and this is my first time creating a video for others) I need all the clarity I can get!

PS: I am using pre-existing footage that is 610 x 360. I know I will lose a ton of color (and content) given the above dimensions and the effect of projection, but anything else I should anticipate?

Many, many thanks!