With a medium or better attention to detail and some patience, you can do as you did and get good results.
Since you already have strut plates installed, this helps a bunch with the alignment as do the self centering drill bits.
The screws for your machine are probably a betlts/suspenders type of thing.
Maybe you should re-run tests you’ve already done and see what impact the screws make now that you have both screws and plates.
Regretfully, all my prior tests were with both strut plates and these screws. I’ve dealt with sickness, joint pain, way to much on me, lack of time, etc, and so I just could not muster the motivation to try to get “before and after” testing done. So sorry.
I’ll keep you in my thoughts, Doug. That’s a lot to deal with.
I hope you can unload a bit of that heavy responsibility that’s on you as well.
Have you actually tested that yet. I have not. I assume it makes a difference but before we go telling people it does it needs to be tested.
He says he did not. I say just put googly eyes in those holes and you are good. 
Can we take this sentence out please. I really do not want all the new user Thinking they need to do this. I am not convinced it is super easy to keep dead flat (It wasn’t for me) and I am not sure if / how much it helps.
I left the screw holes in just in case when a couple of us get a chance to test and confirm I will either leave them in or take them out.
I also think a #8 screw might be a bit big. With a screw that large your hole need to be perfect as those leave no room for tiny misalignment.
I am hoping to find time to rebuild my Full sheet while I am off this time. If so I will leave the screws out of it and run it for a while, Then I will go back and add the screws and see if I can get any noticeable amount of difference in a large beam. I did put them in on one of the beta runs and I didn’t find a noticeable difference on a 36" cut area.
I’m guessing we need to test this sort of stuff in aluminum at this point. Finding differences in wood with a 1/4 endmill is not going to be easy to see anymore.
Sounds good. I need to make some aluminum cuts with the LR4 anyway’s LOL. Who wants to buy a set of Aluminum LR4 Struts so I can see if its even worth offering 
I have not tested it. I removed almost all the details from the post, and let it just be a statement and a couple photos. I added a disclaimer: “I have not tested whether the machine is stronger with these than without.”
Too soon 
Perhaps a spring scale pulling on the endmill/gantry and a dial indicator, with and without the screws in place.
At some point, one of the XY/YZ “Plates” are more likely to lift than the Beam deflect, I found this when mistakingly using flat tipped V carve bit 
and some downcut jobs on my LR3. Recently started thinking about strain gauges on YZ being needed when Beam deflection isn’t the bottleneck.
The only remaining instance of the part that needed removed, is in your quote of it. If you edit that and remove it, it will be gone. 
Love this, but I’ve been planning on cutting my own aluminum struts. So, question for the braintrust is - How thick does the aluminum need to be for rigidity. I’m thinking I’ll cut a 3 mm piece of BB ply or hardboard and paint it, then cut a 3mm aluminum piece for a total of about 1/4"? Is there any measurable advantage to going thicker on the aluminum? (At that length it seems like thicker will be quite a bit more expensive.)
Curious why using both 3mm Alu and 3mm Ply/Hardboard? Personally planning to just have 3mm Alu.
Doug’s setup does look pretty solid to me though, being already primed is a nice bonus:
No reason. Mainly as a spacer/potential contrast color if I mill any lettering.
I may just do some laser marking instead. Also, I do want to look at the light pipe mod.
Why both? The wood will be completely null if you are using aluminum. The most you can go is 1/4". but I think you would be good with 1/8" or 3/16" to save some cost
Yeah, they’re cool, haven’t milled Alu plates yet, partly because of this. Maybe we need a dedicated LR4 Lit and pimped out topic?