@Tom_Oyvind_Hogstad Carbon fibre will not work. I’ve tried it with high-temp UD carbon, but even that starts to creep and warp at the high temperatures we’re dealing with. And, of course, it’s ridiculously expensive.
Bed weight isn’t much of an issue for me - even my heavy 6mm GFK base is being tossed around at decent speeds.
@ThantiK sorry to bother you again. What thickness aluminum are you using? I’ve got a sheet of .5mm sitting around, waiting to serve exactly that purpose.
Ah, ok. Missed that post.
Thank you for the info @ThantiK I have been wondering how one attaches heater pads, and what the advantage is. Thin glass becomes a much saner choice as soon at it is on top of a truly flat surface with even heating and not directly on PCB heated bed … Currently I’m struggling with missing Z steps or lumps of extrusion that the hotend crash into and ruins the print. Drives me insane as I think I have tried pretty much everything to fix it 
@Tom_Oyvind_Hogstad When you say UD do you mean the entire laminate was unidirectional, or was it just made out of unidirectional fabric and the layup schedule used multiple directions? Could you link me to the exact carbon you used? The proper laminate (which may be expensive) should give a zero or very low CTE if properly engineered.
@Christopher_Benjamin This is the carbon sheet i used: http://www.carbon-vertrieb.com/shop/CFK-Platten-hochfest:::12.html .
@Thomas_Sanladerer Thanks, they don’t give much information, but I’m under the impression that thermal expansion is not being taken into account with those laminates.
I got several pieces of 3mm glass to replace the 2mm my printer came with. I have found that it heats a little more evenly and the extra thermal mass keeps abs stuck a little better. It also lets me get printing quicker if I have another surface ready to go after a print finishes.