It is the weight (and windage) of the sail that is an issue. Most boat stability is calculated with no sails up the stick.
The weight of my Harken furler, in total, is less than 17lbs. The majority of the weight including the drum and its mechanism, furling line, tangs and apparatus that make it up are at the BOTTOM or deck level. Close to 80% of my furlers weight is within 14" of the deck...
At best I added maybe 4 lbs. aloft. Contrast that with the weight of in mast wiring for antennas, wind, anchor, spreader lights and a tri-color and you're way, way over 4lbs. and that's just the wire no antennas or anemometers. I'd bet enough bronze hanks, for a traditional configuration on my boat, would weigh at least 2 lbs!
Heck if you switched from the standard wire halyards, of that vintage, and replaced them with modern day low stretch line the extra two pounds aloft for the furler would become a net loss. In other words replacing your wire halyards and adding a new furler, to an old boat, will result in less weight aloft than the original configuration. Beyond that even 15 pounds on an 11,000+/- pound displacement boat is negligible.
Hell, most radar mounts, forget the dome, weigh in at more than 3-4 lbs.
Remember this guy has an older Bristol NOT a Mumm or J Boatn so weight aloft is really not even worth talking about in his scenario...