I did not know glass and mag scales could be combined on the same DRO installation.TouchDRO is popular here. There is a dedicated forum. The owner/sole proprietor is active, and loaded with valuable knowledge. He skews toward glass scales. I went glass for the bed travel on my lathe, and mag for the cross slide, because it's smaller. I'd go glass for all, if there is room. You can find good prices via a variety of sources. Or, just buy a premade kit from china. Lots of options.
Is there a trick to it? Can you tell me more? Point me to documentation?