Or maybe the other way around - make the root of the inner arc of the left shape straight?
I might be talking nonsense. just thinking out loud.
Heh… I hoped nobody would notice that if I didn’t attach the actual file. 
I need to adjust the arc a little over to keep the “L” intact. Purely aesthetic though.
Also, the adhesive is https://www.amazon.com/Gorilla-Heavy-Adhesive-Multipurpose-Repositionable/dp/B0752XM8VN
I like your design.
Looks like i need to add one of these to my adhesives GlueBox
Great work Rick and thanks for sharing your design. Much Obliged.
This is a small test out of cardboard. looking very good. next i will cut two sizes (big and small) from Acrylic
I also want to make one, thank you for sharing. But I don’t understand why it has the curved shape instead of just a long slit. I certainly haven’t been aware enough, obviously there is a logical explanation.
For me this means better view of the piece being centered and for making sure the pen’s tip wont wobble as you can tilt it and force its way safely along the straight line. a cone pencil tip needs clearance to go through a tight slit and that can and will have a negative effect on the accuracy of the center point.
What “cardboard” are you using?
Where’s my royalties?
Have your attorney call mine 
“That’s a derivative work based on material that was freely shared.”
Rick, cut this out 
and save it for good and when you come over here once, call me and get it swapped for one or two real beers 
I found https://www.amazon.com/gp/product/B0849TLDNB
About 1/3 or 1/4 the cost of acrylic and reasonably thick for testing. Thanks for the pointer, @Squid
EDIT: Fixed the math above. Cost is about 1/15 that of similar acrylic. $34 for 100 sheets of 12"x12"x1.25mm chipboard vs $500 for 100 sheets of 12"x12"x1.58mm acrylic.
Sorry, @bernd.dk I can see through that 
, therefore it must not be very good. :P.
This is my current, “That’s the good stuff!” https://dragonsmilk.com/ 
it looks delicious !!!, maybe I should come over to you and trying your beer 
Skål
Refsvindinge is located on my island and is a very small cozy brewery, I picked up beer and enjoy beer in the brewery with the brewer.
But what you have found is a strange marketing, perhaps adapted to the English market. Just this beer is way too heavy for me, but they have nice other beers too.
Skål