Hi TJ
I like your web sight, looks like you have fun doing what you do. Now about the weather vane. I personaly have not made one, but let's just look at the basics. Your grandfathers vane mounted ontop of the barn was more than likely an arrow. you had the point for the direction of the wind and the feathers (virtical) acting as the sail. The wind would push against the feathers from the side until the arrow was pointing into the wind. I'm thinking that you have 2 problems. 1st your balance point is going to be closer to the back end of the vain, I don't think that is bad. 2nd it looks like they are going tobe top heavy. So when you mount them on a rod you are going to have side friction from it wanting to filp down. One simple way is to put a counter balance on the frount, downside, close to your mounting rod. just for an example. You can think of ways to make it decrative. If you use a bearing I would use one like they use for the deck of a lawn mower, for the shaft. Graffite impregnated metal rings.
I hope I might have been a little help. Good luck!
Roger