pink

We have a house which is 40 years old and I am doing a major alteration. Especially the existing ceiling rhino board. The ceiling joint has three quarter timbers and this has been painted with PVA. I have moved the three quarters and I can see in between the ceiling there is a gap. I want to Rhinolite, but it worries me that at a later stage, the cracks will appear. Please can you give me some advise on what material to use, before Rhinolite. e.g Silicone or ceiling tap...... What else?