You can slowly sand down bits of the shaft.
the main difference between the stock flute and my flute is that my shaft is wider, inhibiting gas flow.
you'll need to preserve more of a rounded shape, but if you can thin down the shaft, towards the top ( piston end is bottom) in a tear drop fashion, thin towards the middle and near stock at the top, it should allot more gas through.
Give it a shot, if not, I can mod one of my spares and send it out to you, if you cover shipping.