Yeahh dude its recommended you do not shave ''good hair'' and replace it with wig hair to create the most realism. Make sure your base only covers the white part you've shown in your diagram.

Theres nothing stopping you from changing your mind if you dont like it and going with a bigger base. As long as its shaved before attachment there isnt really an unmanagable hair related mess with glues or such. Atleast for me