Ditto on using sealant alone instead of a rubber gasket. Using a good sealant should easily seal out water whether on the mooring or underway while the loads flex the structure.
In my former life I worked on aircraft. A miserable job handed to the lower seniority techs (me, at the time) was repairing/replacing the cabin windows during the phase inspections. Needless to say Boeings and the other airliners have a lot of windows...
The windows are thicker than what is required in the marine industry (Learjet windshields are three layers over an inch thick) due to cabin pressurization, possible bird strikes, and the extreme temperature and pressure operating environments, but straight sealant is used and when properly done seals cabin air pressure from leakage at over 10 psi cabin pressure.
Depending on the installation, some windows requiring drilling while others have a mitre external surface that positions the window on the inner skin surface. Bits specifically manufactured to drill plastics are used to drill the retaining screw holes through the window due to chipping and possible stress cracks that may not be immediately visible wood/metal bits may cause.
Once the window is trimmed to size and retaining screw holes drilled - oversize holes as mentioned, a coating of the sealant is rolled on both inner and outer window surfaces, the aircraft skin, and window retainer mating flange).
The screws are coated with a good helping of the sealant and inserted into the screw holes while a helper installs the washers and nuts. Once all are inserted, they are first tightened until snug (using a cross-torque patter - evenenly on opposite positions similar to tightening your wheel lug nuts) then the final torque sequence is applied to the nuts/screws in the same pattern. While tightening the fastners, the excess sealant oozes out of the surface sealing areas and screw holes making a water and airtight seal.
The sealant is cleaned from the surfaces with MEK prior to setting up but, extreme caution must be used since MEK will easily damage plastic, fiberglass, melt you sneakers, etc.... and could damage the window or
paint and fiberglass surfaces of your boat. Leaving the protective film on the lens surface and taping them and the adjoining cabin surfaces with several layers of good masking tape will help insure damage will not occur.
Although I have not used this sealant yet on my boat, I have purchsed several tubes to seal the LARGE side windows on my Conyplex during my refit project. I chose to use this type sealant since it is verry strong. It is also used on the wing stringers and rib to wing inner surface skin surfaces to form the integral wing
fuel tanks. It is so strong, having a failed rivet or other fastener where it is used, the surfaces will still be in shear and held together. The sealant is a two-part mix, called Pro Seal with a P/N of 890 BX. The number in the X position = cure time in hours (1/2, 2, 4, etc.) available in several tube sizes and can be purchased from a aircraft parts/material supply stores.
After reading the Solar Stick thread I must say, I am not in any way aligned with the sealant manufacture. I'm just an everyday sailing nug applying differnt processes leasned along the way.
Happy Sailing