Greg, this fall we set the Triumph on a platform with the suspension sag it has when I am on it. I took a foto of the front of the bike. Then we took some straps and compressed the suspension 1.5 inches. Then I took another photo. Both pictures were enlarged, adjusted so they were the same scale, and printed. They were compared. The frontal area reduction by lowering was the 4 inch width of the front tire x 1.5 inches, or 6 square inches, total. This tire frontal area has a rounded and streamlined shape, so its reduction does not significantly improve the aero.
Really fast bikes will benefit from this frontal area decrease. Bikes with the speeds of my Triumph (less than 150 mph) will barely notice it. Lowering the Triumph, based on the calculations, is not worth the trouble. It remains at its original height.
Good luck with your A65. They are a much better bike than popular opinion would suggest. In many ways, they are better than the Triumphs of the same era.