Ah! It pays to have been in a military style marching band in High School!
I was just doing a search online to see with what I could fill the cavity of my new plaster body cast my husband helped me make the other day.
In order to NOT get faint at all while standing for the long session, you MUST keep your blood pumping back up through your legs! To do this, first, it is very important that you space your feet apart (at parade rest, if you please) almost as far apart as your shoulders are but not enough to spread your hips wider, of course. Next, ALWAYS wiggle your toes and, if need be, tighten and release leg muscles throughout the duration! The toe wiggling is the most important. And do not lock your knees.