It really isn't much like the 1968 -1970 twin shock drum braked Eglis, to be honest. All sorts of weight claims are made for those but in reality they are all around 400 pounds dry , give or take. To really get the weight down I had to use modern wheels and suspension, which also gave the benefits of better ride and braking.
The weight in the article is listed as 350 dry, however the new motor is 11 pounds lighter( belt drive primary and light cover)planned exhaust is 4 lbs lighter(titanium) and forged mg wheels are 10.5 lbs lighter. This will put the finished weight with oil but no fuel at around 325 lbs. After that, it is just grams here and there that can be removed, so that will likely be it. There is only so low you can go when using a big heavy lump like the Vincent, but it will provide a very good power to weight ratio.
Glen