How much overlap have you got? ie from the inside of the cutout in the cabin side to the outside of the window pane? If you have 20-25 mm, then the best way seems to be to use glazing tape around the cabin side to hold the window on. Then, mask carefully level with the outside of the window, then fill the gap between the glazing tape edge and the top[outside] of the window - hope that is clear. The glazing tape not only holds the window on firmly, it provides a 5mm gap for the adhesive sealant.
There appear to be plenty of different sealants about which would work, but the only one I have