I got two sticky sheets with my knp. one had a paper type surface the other plastic. Currently I have the plastic sheet stuck to the bed and I use pva gluesticks on top of that. Works really well.

Haven't added anything to thick to the knp - but I do have an extra 4mm on the flashforge creator and ahd no problems adjusting bed down that much just with bolts.

You could also simply add the correct z-offset to your slicer.
You might even be able to add it in in the firmware from the control panel. Have to admit I've never looked, but should be in there somewhere.