Ok so I measured out a 48" Rump and set up the kilt to have 13 - 3" pleats and a 9" Over Apron.

I just finished bar tacking the pleats at the fell line and measured it out. From the edge of the Over Apron to the edge of the last pleat I get 49 and 3/4 inches. 1 and 3/4 inches greater than my rump measurement. In the instructions it says that up to 1" over is fine (as a maximum) and I would be within that 1" based on initial measurements except that when I "A" shaped the Over Apron it added a full inch to the rump at the fell line.

Is the 1-3/4" going to be an issue with the final fit, or should I fix this before tapering?

As I see it I have two options if I need to fix it: 1) I shrink the Over Apron by 1" to 1-1/2", or 2) I take out a pleat and increase my Over Apron by an inch.