Just tried my first passthrough design using the ruler linked in this post, but they didn’t help me for some reason, some logic error on my part, and my visible area is a bit different. It got me thinking that the best answer is a sacrificial guide that can be scored as indicated in this post. The guide can be reusable and needs to be positively anchored to the tray or as written above, to the device chassis. Got me thinking about ways to attach to the crumb tray more securely. The guide does not have to be up against the side, so a simple rectangle with room for a 10" measure (scored in the first tray cutting) and holes spaced for dowels at a known distance that fit the crumb tray would work every time. So here is my design:
It’s a rectangle with two cutouts at 9" O.C. (on center) which lines up perfectly with the honeycomb tray. The cutouts are for Honeycomb pins (a remix of the original). You can use the original on some materials but I added extendo pins for .25" and .125" material and will work on thicker stuff for your guard.
The idea is you can cut out the guide and a pin or two if necessary. Then pass through away!!
125|19x11
Well, I can’t figure out how to upload my design (doesn’t seem to work) so I uploaded to Thingiverse (link below). Credit to @eljefe4 for the pins!
Nice solution. As long as you don’t move the tray you’re good to go.
I’ve found a way to fix tray movement. It’s using a round, ridged scrap that just happens to be the perfect size to wedge into the front right gap, and the tray is always firmly in the same place. I keep meaning to produce an SVG to share…
Yes please…mine goes walkabout a lot with the shield removed. 
Can anyone tell me why, just casting a small amount of epoxy, or similar, into the pre-greased dimples, then dropping the tray in, to give it perfect fitting feet, would be a bad idea ?
John 
Hmmm…
It would be really vulnerable to any kind of dust / debris getting in there and throwing things off-level and stuff. That’s all I can think of.
I discovered the YY alignment can be off if your honeycomb is not perfectly manufactured true in the X and Y directions! So a first pass should be to cut a YY line along the guide, and then remove the cut off so your guide is perfectly aligned with the machine YY axis, then start the fiducial and pass through cutting. Important!
Okay, so I got out the calipers last night and went to town… 'Twas fiddly with all the curved surfaces and hard-to-reach crannies, but I now have a nice pair of “boots” that keep the tray solid as a rock in a consistent location. Will try to do a writeup this evening!
Yay! That’s gonna beat the doubled up tape that I wedge down in there when I need to keep it stable for a print without the PT shield. Muchas Gracias! 
That’s a great idea, especially if you use @timjedwards “boots” and let your own machine cut the right edge along the Y-axis for a custom edge.
Same way I cut a bump stop for my cnc
Jules,
You use just regular plywood in your glowforge??
Thanks,
Sometimes. I really prefer the Proofgrade though, it’s just a heck of a lot easier to cut through consistently. 
Thanks,
I really like the proofgrade also. I didn’t know if it would ruin the glowforge using regular store bought plywood.
Nope…but you’re going to have a terrible time cutting it compared to Proofgrade. It’s full of knots and glue plugs that will keep from cutting through - I ruin about 50% of the cuts on cheap plywood, even trying to avoid the knots. There are just too many hidden issues inside that you can’t see.
Thanks for the info!
I will keep buying the proofgrade then 
Well…you can try it…just don’t expect to get the same results. (Buy a lot more than you think you’ll need for instance.)
I’m spoiled by the PG, but it can be useful for support in large boxes where the interior doesn’t matter as much. That’s mainly what I use it for - the large sheets of PG are expensive.
They are expensive.
Still trying to understand the pass thru.
How long have you had your GF?
For my own machine…it’s ten months now. But I tested a PRU unit for nine months prior to that. So just over a year and half total. (Time flies!) 