Hello sploo.
In our main business (
www.capeboatworks.com.au) we cut Marine Plywood every day. for plywood 6mm and less we use a 1/4 Solid Carbide upcut 2 flute and cut at 400 IPM , one pass and nice clean edges. Sometimes with plywood you will get some chip out across the grain but it is minimal.
For 9mm and thicker ply we use a 3/8 2 flute upcut as we need a stronger bit at those speeds otherwise they just snap.
When we have to cut plywood 15mm and above we do the cut in 2 passes using the 3/8 bit. 3/8 is about as large as you would want to go without having a larger HP spindle.
Keep the feed rates up as fast as you can.
Are you using Mach Quantum???.. Since switching to Quantum the quality of our cutting has improved because Quantum slows down and produces better curves and corners.
Hope this helps.
Cheers
Frans