This is the response from Warp Drive when they were asked about shortening the prop.
"Yes, the propellers can be cut down in diameter. Everything we build starts at the full 72” diameter and then is cut down to the specified diameter. You would end up cutting 5” off the ends of the blades to change a 70” prop down to a 60”. The main issue is balance. If you have a way that you can set this up to accurately trim 5” from each blade, your balance should stay close. You can use a miter/chop saw with a stop or clamp set at 5” so that you are taking the same amount off the end of each blade. After cutting them, you would simply need to sand the rough edges with a sanding block with 120 grit paper and you are ready to go. No need to seal or repaint the ends after cutting. If we trim the blades down here, we would balance them on our digital scales just like a brand new prop. This would run only about $45.00 plus freight for us to trim and rebalance."