Duh... I had tried everything with that little lock pin, except simply pulling it out. That did the trick.
Thanks Neil!
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SSIdiver02,
I agree with you that reg maintenance shouldn't be taken lightly, and I'm not trying to save a buck. I just had my reg in for annual service by a professional, and got it back with a new-found tendency to freeflow. I checked that the intermediate pressure from the 1st stage is within spec, and I believe the 2nd stage is just slightly misadjusted. I can either send it back for another week, or probably fix it myself in 15 minutes.
You might be able to do this through the side port, which can be opened with a 6mm allen wrench as you said. But I wasn't able to fit a tool through this narrow opening to make the adjustment, hence the need to open the front.
Thank you too for your input.
-Nudi(branch)