Customer wants to have hardwood in doorway cut out and a pre-fab composite stone dropped in the void as a threshold/or transition. This goes from a hall into a bathroom with composite tile. The hall is 3/4" oak over shiplap at 45 degree angles. Joists are on 16's. I'd need to cut out the hardwood to one side of the jamb and cut out a bit of tile and plywood on the bathroom side of the casing. If I removed the hardwood and plywood what would I use as an adhesive to support the Stone? Silicone? The pre-fab transition has rolled edges, so it looks as it was made for this type of project? Stone is 3/4 and so is the floor, so it can't be mudded in.