Making a slow fill valve?

[3crows]

I was not especially worried about over filling when I was running 3,300 psi aluminum 100 cf scuba tanks or my HP100 3,450 psi steel scuba tanks. But now that I am filling from a 4,500 psi SCBA tank I am. I had already threaded the internals of my fill whip to install two Allen screws to restrict the flow to only that which can squeeze between the threads. But despite the slow fill of my whip, with 4,500 psi behind pushing, the air flow is somewhat more than I feel comfortable with. I am thinking at next opportunity to pull the 300 DIN scuba valve and either install a restrictor at the dip tube or inside the valve itself. My concern is causing the compressor (Yong Heng) to work harder. But the output of the YH is not so great that I think the compressor would not notice the restriction, the restriction to the compressor being working against the 3,000 to 4,500 psi fill requirement. Any opinions on the restriction vs the compressor or another way of restricting flow?

Standard SCUBA and SCBA valves are for life support and have a high flow rate of approximately 60 plus cfm. I want to cut that down to a controllable amount.