You can find complete how to upgrade article on my site: http://lensdigital.com/home/?p=1498
SH-G350 a.k.a. 50W Chinese Laser cutter from eBay comes with 800mm CO2 tube that fits nicely inside machine. However you can upgrade your tube to more power, but this means longer tube that will no longer fits inside. Fortunately machine has cover on the side that can be removed and longer laser fitted.
This enclosure easily fits 1250mm/ 49" SP 60W tube, with room to spare!
I want to credit this design to Jeff Body. I just modified it very slightly, created a 3D model in Sketchup and sharing it with the world.
You'll need to cut it from 1/4 (5.8mm) acrylic. All pieces were glued with JB Weld #16. Once it dried I attached extension to the chassis with 4 very short 1/4" machine screws and nuts.
I also added a grounding strip inside which is basically an aluminum tape used for HVAC. At one end I attached paper clip to it with soldered wire and screwed wire with one of the machine screws so it grounds to chassis.
There were concerns about UV light escaping thru clear acrylic, so I built a UV detector and there was no UV detected. Fluorescent bulb inside machine generated more UV actually :)
As you can see in this video: https://www.youtube.com/watch?v=GxJ3ikYPjuM