Thank you, Stan. Your second pic shows the safety int he middle position, and clearly shows the the forward part of the T-bar...which is exactly the dimensions I found with trial and error with a 3d-printed version. Here is my safety selector in the REARmost position, with triggers and plate installed.
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As you can see, I have just a bit of slack to take up by adjusting the link of the bar. It has a notch/recess in the bottom into which I believe the trigger pin passes through snuggly.
Here is the forward most position.
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It doesn't quite make it far enough forward to clear the safe position, and cocking throws the bar past safe all the way to the rear position. The picture looks like my block is pressing agains the receiver, but it is not. Without the block, the bottom of the safety bar shows the same position. So I need to do 2 things (iteratively). 1) adjust the slot in the T-bar a bit to the rear, and gently form the link of the safety bar to take up the slack so its notch meets the trigger pin. 2) I need to remove 1-2mm of material from the forward most part of the safety where it enters into the receiver and contacts the bolt guide block.
I got my initial measurements from al's album of parts, since his photo was on the back of wrapping paper with a 1"x1" grid. I got within ~0.3mm of my final attempt (took 3 tries, 4 if you count the final rendering tomorrow. once I'm happy with the safety bar rear position, I'll adjust the slot in the bar to be perfect.) The same picture shows the forward pin of my safety bar is upwards of 2-4mm longer. Sorry for not using inches...I used freeCAD, which is set in mm.
Funny, my 3d print T-bar is working find. I stress tested by squeezing the triggers pretty hard in the safe position, and they didn't even deform. They will fail from friction of sliding, though, eventually. Once I get everything perfect, I'll make a steel one.
I'm as certain that I have a Lewis gun as whoever made the serial number tables. I'm at 76,xxx, well into the Lewis range. My safety parts match your's exactly. Al's selector looks a bit different than ours.