Really....test it with a flickertest. Your image on the wall is so small compared to the screensize of your final project. A hardly recognizable 1 cm image displacement now.... will result to a way larger problem later.
He thinks doing 10GB into a 10GB switch into 1GB outs just magically split and scale all the packets perfectly in time.
You've pointed out the flaws of being too close and not the real setup. He doesn't wanna listen and its gonna really come back and haunt him when he gets seams on show day.
Now if the client doesn't really notice, the content is slow moving or the surface hides it, might be able to squeak out of it.
But if you strobe and film it, i bet they're all over the place. Sometimes you can't get video cards to lock their outs if they're gamer cards. Let alone 10 different unsynced packet based boxes.