Just to come full circle - I created my first batch of 32% nitrox today. It ended up being 31.6% but my target was 3000 PSI and I went to 3200 PSI thinking since I was going to test it I wanted to overfill. So I know why I was off and what to do next time.
The Voodoo Black Magic mystique really got to me. It took several hours and maybe even a full day before I got the nerve to connect the O2 and actually flow the gas. The needle valve really only wants a crack - so I filled too fast at first but I am getting used to the gauges and the valve.
I did not burn down the shed or blow anything up and now I feel a bit better about having done it...
Thank you to those that offered guidance and opinions - I needed to hear it and I had to try for myself in the end.
This should be the beginning of $1.05 fills for nitrox...