I built a 2m x1m one on a carcass/box plywood construction but kept the top same design with the 20mm holes on 96mm centres and torsion box type style underneath with the oval holes. Have castors on it and move it around a lot, it's my main bench and gets used and abused. I think it's great, I don't use the hole with parf dogs or any thing, just clamping ability. All pocket holed from the under side and I went with 12mm birch... Next time I'd stick to MDF as the ply splinters etc and catches when used as an assembly table.
I bought a hospital bed off eBay that when I get time will become an assembly table/back bench with no holes in.