I recommend anyone wanting reduced pressure filling invest in a HP regulator.
Get one that will do 6,000psi inlet and 0 to 3,000 or even 5,000psi output.
That will keep the safety shutoff intact and seperate from the reduced pressure you need.
Set the reg at 3,000psi and fill to your hearts content.
The bottle will have 3,000psi in it and the reg supply will go up to the shutoff and stop.
I am going to do this and I beleive there is an additional gain. The time that the spring arm slaps at the switch will be very short as it will only build pressure into a small volume upstream of the regulator.
'Tis 'ow 'm gonna do it
Walter....