I'm considering replacing the forward windows on my 1977 O'day 25. Recently, on a cruise to Niagara on the Lake Ontario, I noticed a fleet of one-designs, Sharks maybe. Many of the owners replaced the porthole windows with pieces of what appeared to be tinted plexiglass, cut perfectly to fit the portholes. It looks like clear marine grade caulking was used. Does this seem like a reliable, cost effective alternative to expensive porthole windows? Thank you in advance for your replies.