Depends on what look you want to achieve.
I have to alter from from mid thigh all the way down to the hem to slim down the trousers. Leg opening diameter was slimmed down from 25 cm to 20 cm (approx slightly less than 8 inches).
I had to take fabric off from the back of the trousers to slim down the generous fabric from the front rise, and was very careful not to take too much so as to not alter the look of the pleats. The end result I achieved was more of a straight cut look (Base A) from the thigh down but the front rise fabric is still abit generous but not ridiculous. Overall, I love how the trousers look but just doesn't seem right with a suit jacket.