Are you sure your rim is radially true? A high spot might be the tire or might be the rim.

Stretching on a clincher rim at max pressure is a fine idea.

I never have any air in the tubular tire when I'm putting it on the prepared tubular rim; it's way easier to make little shifts in the placement with the tire totally flat. Then put in enough air to give it some shape and re-check. Then press it up to max and let the glue take hold.