Online metals has sizes larger than 2" in 1/8" wall, but not 1/16".
They also have 3" in brass, but it costs $127+ per foot, so not an affordable option.
As far as I’ve ever been able to find (and I searched for this over the summer for a project we were working on) there is no square tube over 2" that comes in 1/16" wall thickness (or anything like it.) Tube over 2" seems to be mostly intended for structural applications and 1/16" would be too thin as a wall thickness for this. You’ll probably need to go with the larger tube size (2 1/2") and accept 1/8" walls in that bottom tube.
I checked a couple of my favorite sources and I was able to find 2.25" and 2.50" square with 0.095" wall (6063-T52). But it looks like once the size is larger than 2", the 0.065" wall thickness is not available. Maybe that makes sense given that the larger sizes are probably most likely to be used in heavier duty applications.
Just for giggles, I looked at Carbon Fiber square tubes. I was not able to find 2.25" or 2.5" there either, but they did have 0.75", 1", 1.25", 1.5", 1.75", 2", 3" and 4" sizes, all with 0.0625" wall thickness. So, if you really want to score sexiness points…
Thanks for the help. 0.095 wall seems good until you realize the ID square for a 2.25" OD tube would be 2.060". That’s just 0.060" for the string and sliders (and you need a gap too – it won’t slide if it’s line to line and nominal dims are not actual dims so you need some bonus gap for that…)
Probably a bridge too far.
If I REALLY need another stage to make things work and didn’t have to worry about bending to twisting, I guess I could go down one more stage to 0.25" as the final stage but that is about the end of the road for this style nested actuator.
I am printing the parts I need to evaluate the design now. I will post an update if it comes out well.
Thanks again for the input. CD community always comes through.