Ok I see your point now. You having worked with all those printers in the past, it is I that I should be asking you how-to questions in then end...
But any way, I personally have printed up to 11 inches long PLA parts with no warping issues. As far as PETG the longest parts that I have printed so far is 7 inches, and that with no problems. Any PETG parts bigger than that I do not have a reference. Now, I should tell you that I did have tons of problems in the beginning when my printing bed was a disaster. Meaning, the print bed, had a mind of its own when it came down to getting it level, and actually remaining level. Once I upgraded my bed, leveled it, determined the average variance in height, and set the proper first layer height I stopped having warping issues. I'm sure replacing the Plexiglas print surface with a borosilicate glass made leveling the bed a more reliable process.
The same with ABS as well. Yes I have printed parts up to 6 inches long (successfully) without using a heated bed ( I do not have a heated bed). With ABS I use Rafts quite a bit, and with PETG I found that 3 Brim passes and a hot first layer ensures the print stays where it is supposed to. For me and the esun PETG I heat the first 2 layer to 230 C and print the rest at 226 C at slow speeds, and low accelerations. Also, I make sure that the room temperature not to be less than 74F when I print ABS or PETG.
With that said, I believe to have found a secret weapon when it comes down to a tackifier compound for the built plate. I swear by Elmer's CraftBond® Acid-Free acetone based spray adhesive.
http://elmers.com/product/detail/E421
I spray one very thin layer on the entire
glass bed (this will not work on a Plexiglas bed- it will probably destroy it), and let it dry for at least 5 hours. Then I can print ABS, PLA, PETG, and PLA/PHA with no adhesion issues at all. In fact, I can print 2 to 3 times over the same spot with no adhesion issues. The only problem is cleaning and re-prepping it after it looses its sticking ability. For that I remove the glass surface from the x/y bed carrier and pour some acetone on it and use a razor blade to scrape it off. It comes off easily as the glue is acetone based, but it is messy. I then use fine steel wool dipped in acetone to completely clean the glass.
After the glass-bed dries, which is very quick, I re-spray a new coat with the Elmer's adhesive for my next prints. To be hones I print about every day something, but I typically clean and re-prep the print bed once every two weeks. I typically print smaller stuff. I just move the print spot around either using Cura, or if I use slic3r, I insert what I call a blob ( a 1 cm circle that is one layer high), which allows me to move things around with slic3r. As you know slic3r does not allow you to re-position a print unless you have more than one print item on the print bed.
For me, I have used glue sticks, hair spray. sugar water, ABS juice, and nothing comes close to the Elmer's spay adhesive, except I assume a heated bed which I do not have a reference on.
Any way I hope that I have not shared something that you already know...
its cheap, it works and you can always get it to stick better by light sanding it. its the best stuff going.