I see a lot about ppl complaining of flex on their tubing.
Would there be any benefit to adding ID piloted sight on either end of tube. With a hole in the middle and a piece of copper tube heat set into the middle hole. Inserted this into the end of the tubes.
Then run some SS lock wire through the middle of said insert and copper tube.
Then tie the ss wire to a buzzer or data log circuit/light, so that you can see where and when you have made the tube flex too much. When it flexes too much the taught ss wire inside contacts the copper tube that is inserted into the tubing and completes the circuit making a buzzer sound or a light. Or log it as a counter circuit for the whole job.
Just a couple things I could see helping and you can also dial in your tolerances with different sizes wire or copper tube (mig welder tip etc)
The trick is catching flex in the middle that is the steel, and not the copper in the moddle when ypu mive the machine.
It’s not hard to know when you get chatter, you can usually hear it.
I would fear that tbis sution would end up costing more than just getting thicker steel to build the machine with in the first place.
Yes your probably right I was more meaning of using it for checking alignment and cut depth and speeds for final tweaking.
We use this method for drive line alignment.
If I get some time I will do a little drawing.
Thanks for input 
Flex does happen especially when smaller diameter tube is used. I find flex is more prevalent mid span especially with heavier cuts. Less so with lighter cuts. Honestly, my 2’ x 3’ working area is too big for a mpcnc.
I’ve seen this a lot.
How I dealt with flex issues is simple. 1" DOM, .120 wall. All parts that the DOM contacts or went through, 3 perimeters and 80% infill.
With those settings, with a magnetic base dial indicator, flex is under 0.0003" at very high plunge rate.
My 2 nickels (inflation…)
Matt, my 2 are 2’x4’, and 2’x2’ working areas.
I also run at high feed rates, 120in/min and plunge speeds 20 in/min.
Videos of mine 2 running were posted on the FB group page.
Mine is 3/4" emt… not 1" dom