Yeah, you gotta be careful !!
When I do boost, I use similar method to yourself, but usually 1 layer glue to protect sponge so G BB GG, or G BBB GG,...
As Yogi mentioned the top sheet is generally forgotten, this is at least as important as sponge hardness for the overall ‘feel’ of the rubber (sponge...
Not sure!! I’ll end up giving it a go one day!! If EH Z is softer then it may well suit the sort of feel I like, Yogi reckons it a couple of notches...