Warren,
Those vangs are great for racing. They are noisy though; the spring makes noise when the boom lifts and falls. Go take a test drive first and spend time down below when it's rolling. Maybe some are better than others, but I would not have any of the ones I have been exposed to on a boat where I am trying to sleep underway. I am sure you are aware that vangs in general put a lot of loads on the gooseneck and the attachments at the mast and boom. They can cause the boom to break at the vang connection when the boom snags a wave. You got all the way around the world without one, why add it if you don't need it? They probably cost as much or more then the main you are trying to protect.
If you have not already, replace your topper with thin ~ 4mm spectra. It is way easier on the leach than even coated wire because it is soft and has less inertia. The bungee system helps keep it off the leech without adjustments. It's cheap too (way less than a main) I replace it every handful of years to keep it fresh and worry free.
I am with you about boom movement. I have preventers ready to go all the time. I have lashed big blocks to the stanchion bases that are just forward of the mast on both port and starboard. That lead creates the same/similar angles as going to the bow cleats, but the stanchion bases have four bolt and original bow cleat only two. The line has a quality high load carabiner that hooks to the mainsheet bail and the other end leads to secondary cockpit winches. A cleat at the cockpit end would suffice. The port side secondary is my furling winch, so I often use a cleat on the outside of the coaming for the preventer. These lines are also used for the pole after guy. Jibing requires swapping them, but I am not racing around buoys, so I live with that con and most designs require swapping the lead. I furl the genoa up and center the main pre jibe and then take my time. I love that they are always ready and it helps with the motivation to put it on as soon as the boom is eased from close hauled. They work great as a vang too, although I find it's usually faster without vang unless you are running. More twist is less weather helm, so less rudder needed on most reaching angles.
Dave,
Sorry if I sounded edgy with my wheelchair comment. Respect to you for making your boat the way you want her, and I understand the motivation to keep it all in the cockpit. I was anti jib Furler when I was a teenager, I would not cruise without one now. I was 20 years younger when I made all those rigging decisions, got things working well and have not messed with them much since. If I were gearing up to do a bunch more shorthanded distance sailing, I might revisit leading things aft but having dealt with the drag, spaghetti and lines under foot on other boats I doubt I would go there for our little boats even as I age. As you are finding out adding single line brings even longer reef lines, more drag and challenges tightening the leach reef. It looks like you are on the right track to sorting the system out.
Railings at the mast now that could keep me sailing longer. Honestly, we are mostly weekend warriors now with winter trips to Florida or Bahamas happening every three years or so. We mostly just "lazy sail" with genoa alone unless we are going all day.
Oh, and I am starting to look at power cat and trawler listings......I have been windsurfing lately for fitness and mental health, and it scratches my sailing itch, so I am starting to consider trading the sails for a big rectangular bunk rather than the "snuggler" up front

I may not do cruising sail forever, but I will always be on or in the water. I move slow too, it maybe another 20 years before we sell or give Sayonara away!
Have fun with projects mates!