tile backerboard

Evening, I have tile backer boards (floor to ceiling), then a wall to wall shower tray fitted with a classi plus seal. The instructions on the classi seal say to use tile mortar to fix the classi seal to the backer board. Trouble is I'm taping and tanking with the aquaseal wet room tanking kit...

Evening, I've got myself in a not-so-ideal scenario. Bathroom is 1.8m wide, I've a shower tray which measures 1.8m so it's going to go wall to wall. I have studded the wall using small 200mm batons (I could have used dot and dab but that's where I'm at). I'll be using tile backer board and...