I have developed a removable glass bed system for the Taz 5. (probably work for the 4 also). It is an aluminum tray with magnets designed to hold a square glass bed with ABS handles for easy removal while still hot post print. I use hairspray and an enclosure, which works fantastic. But there is no reason why you couldn’t cover the glass with PEI (Or anything else) if you like it (I hated the PEI bed).
This is a huge advantage over stock because you can remove your printouts to let them cool quickly, and removing the part will not throw the printer bed out of level. You can also use multiple glass trays and swap them out as you want.
I will be offering kits for sale here and on thingverse soon.
Kits will probably run in the neighborhood of $400. The only mod to the stock printer (besides the obvious removal of the stock bed) is drilling some 3/16" holes (4x) in the existing aluminum Y travel plate for mounting of my aluminum leveling tray. Leveling is achieved via two knurled thumb screws at opposite corners located under the stock Y travel tray. The glass is borosilicate and can be 1/8" 3/16" or 1/4" thick. Thicker is sturdier, but takes longer to heat. Also the Z knob adjustment screw needs to be modded taller since this tray sits slightly higher than stock. User installation can be done in less than an hour. Minor tweaks to the heated bed PID value is all that is needed in firmware. Otherwise the printer operates as stock.
The entire bed is clear of obstruction so the entire print surface can be used regardless of type of extruder or even a dual extruder. Nothing protrudes above the glass surface, anywhere.
PEI can be omitted (with the use of enclosure) so no more hopelessly stuck parts. Use hairspray for trouble free adhesion.
But any type of surface can easily be added to the glass.
Multiple glass trays (perhaps with different surfaces) can be kept on hand and swapped in seconds. The only adjustment would be the Z knob. Actual level would never change with change of glass bed since the leveling portion never leaves the printer.
Glass held in place by powerful magnets pulling down creating friction with the silicon heater pad which is in direct contact with the glass. The tray won’t move unless you want it to.
Easy to remove glass beds can be lifted out immediately post print without tools for quick cooling and MUCH easier part removal, all without altering bed level in the printer.
Leveling the bed is much easier than stock. Can be done in just a few minutes.
See photos in post below. Please reply so I can gauge interest and answer your questions.