Here's a pic of my redneck shooting parlor. The steel extension in front, with magnets, is for the chrony and pivots out of the way for non-use. On hand stuff/junk all of it. Found the chair in a ditch and the board was headed to the burn heap when I decided to grind the brown, red, black and blue lead paint off to see if it was worth salvaging. Anywho.. the swiveling padded chair with adjustable arm rest is worth every penny I didn't pay for.
Particle board will also sag over time get a couple pieces of 2" angle aluminium and brace from underneath that will stiffen the plywood and not add a ton of weight