I think you may be suffering from unrealistic high expectations, after all at its very youngest your Vincent will be 65 years old. I have related this story before on this forum, but I will retell it in as short form as I can, my Son, now 45 years old, cut his teeth on Japanese four cylinder missiles, but one day for reasons I cannot recall his Kawasaki was off the road, and he was desperate to go somewhere on two wheels, so I lent him my Rapide, with the conditions don't thrash it or crash it, thankfully he did neither, but on his return I asked him how found the experience, his reply was somewhat less than complimentary, his appraisal went something like this " they really should not be allowed on the public highway, the engine is gutless, the brakes, well there aren't any, and the suspension is a bit like when I was a kid and used to bounce around on a pogo stick"
It was all said a bit tongue in cheek, I think he likes it really, but the point is an awful lot has changed with motorcycle design in 65 years, in my opinion not all of it for the better. But the reality is if you want to ride a fantastically fast motorcycle with neck braking acceleration and brakes, fast steering and great suspension, you probably don't want a Vincent.
But I digress, I think it well documented that the best steering is to be had with a 20 inch front wheel as opposed to a 19 inch front wheel, but the variety of tyres are just not available, so perhaps 21 inch is the way to go, but then you get increased height, as I am finding now, dilemma.