I've tested a minireg out and with only six springs, from the piston large end, 2 up 2 down 2up, gives a working pressure range from 200 psi to 300 psi, which is what you want.
The first springs from the large end of the piston should slope away from the piston large end. This way (( )) ((
If you have the lcd manual look at the mini reg spring stack order and remove the 1st of the 3 right hand springs, this will give you the desired spring stack order.
EDIT...... THIS IS IMPORTANT, THERE ARE 2 DIFFERENT PISTON SIZES IN A SPEED OR A4 MINIREG. OLDER MINIREGS HAVE A LONGER PISTON AND HAVE A FLAT SILVER SPACER BELOW THE SPRING STACK TO TAKE UP THE DIFFERENCE. IF THIS FLAT SPACER IS LEFT IN, THEN YOU ONLY USE 6 SPRINGS, IF YOU TAKE THIS SPACER OUT YOU WILL NEED 8 SPRINGS.............WHICH EVER WAY YOU DO THIS ALWAYS CHECK THE OUTPUT FROM THE MINIREG BEFORE GASSING YOUR MARKER UP.
One thing you must remember, there are tolerances in every manufacturing process and you cannot guarantee that each component is the same, so you may find that you get different results for each minireg.