If the center of effort of the sailplan is too far forward, the boat will try and round down first and then the leeway force on the keel will make the boat stand up and hook to windward (not exactly the same as a sail induced round up). The center of effort of both the sailplan and the keel must be in balance or you will have problems with rounding.
The newer harken furlers use the furling drum body as the turnbuckle. One lock nut is below the drum and another is beneath the torque tube. You need to detach the torque tube and raise the foil, release the locknuts then put a pair of vice grips (with a cloth between the jaws) on the swage of the shroud terminal. Then you rotate the furling drum to adjust the length of the forestay. The threads on the upper stud have dye-chem on the threads at the point where you should stop loosening it to have enough remaining threads into the drum. Go to the gear and maintenance forum and read about tuning the rig; if you have more questions you can post them here.
You might consider 3M 4200-UV for the window sealant.