Distillation column design issue--DMF--water separation

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The project now involves constructing a distillation tower for the separation of DMF and water. This is the first time the company is working on such a project. Based on the Chemical Engineering Design Manual, the tower diameter was estimated using Smith’s method, with H=0.35 and Lv=0.008. Using the regression equation, C20 was determined to be 0.06, giving a tower diameter of 1.3. By examining the curve graph, it was found that the minimum value of Lv is 0.02, corresponding to C20 of 0.07; adjustments were then made, resulting in C20=0.086, and the calculated tower diameter became 1.1. Question 1: When the Lv value is less than 0.02, should one use a regression equation or consult a curve graph? Question 2: Since C20 is obtained from the regression equation, is it still necessary to apply a correction for system viscosity? The gas-liquid load values calculated by Aspen are shown in the figure below. The tray spacing HT is 0.4 m, the height of the liquid layer on the tray is hL = 0.05 m, and H is 0.35 m. The liquid load is L = 2.127 m3/h, while the gas load is V = 9896.87 m3/h. The density of the liquid phase is γL = 957.28 kg/m3, and the density of the gas phase is γg = 0.6 kg/m3