I just completed the same upgrade and it worked very well. I upgraded from from a 50 W tube to 90W. I had to add a 14” extension to the side of the machine. I think the key points are all mentioned above. I had to expand the tube from 50 to 80mm while not changing the beam plane. This tube shows two mounting locations and one of the mounts are in the 14” extension.
Burnt thru my glass mirrors so I moved to SI. Even though the beam diameter doubled my 20mm mirrors are big enough.
I didn’t upgrade my 60W power supply because it has plenty of power for materials I cut.
I have always had issues cutting completely thru a favorite plywood and this tube cuts it no problem.
I’d recommend doing it as long as you can get it to fit. Use the same power supply as you can always upgrade that another day.
Just a comment for those interested in doing this. You might have been able to get by with a fan based cooling system like CW3000 for your 40W tube. These tubes require a compressor style chiller.