Fitting the roof of the keep to the exterior walls at wall walk height proved challenging. Also, stress in the roof caused it to rise at the ridge. An incision was made between the eave and the wall walk. The roof then dropped nicely into place.
There is a tip here. If you have parts that are not fitting properly, do not force them. This will only lead to problems furthur down the road. Stop and determine where the problem lies. Often parts have been misglued and you are attemptng to wrestle a partial assembly into place. Look for an inconspicuous seam, joint or corner where an incision can be made. Use a very sharp knife and if possible a steel scale for support. If all goes well, the pressure will be relieved and the parts allowed to move into place. A thin bead of glue brushed out can close the incision.
It's better to get it right the first time, but if you get into trouble, this tip may help you reduce the stress in the model as well as your own!