pro tac removal

I have currently got my first pro tac install after 15 years of fusion and I learned it all here ! I want to take out the bottom two rows to put in some darker hair is this possible without taking the others out? I have used indian remy in an 18'' wave from hair development and it is nice hair,I use the l oreal serie expert conditioner and a satin pillowcase really makes a difference, usually the bottom of my plait feels quite rough but on satin it was like it had just been brushed.I love this forum and I 'm glad i'm not the only one who's a hair fanatic!