PW3 Kindle PW3 5.9.7/5.11.1.1

Hi there folks!

I've already tried searching for an answer to this but I haven't been able to find a definitive one, so I apologize in advance if this is a duplicate post.

I've just purchased a Kindle Paperwhite 3, with firmware version 5.9.7. From what I understand, it's not possible to software mod it on this version, so I'll go for the serial port hardware mod.

My 2 questions are:
1) If I hardware mod the PW3 on this version and then update to 5.11.1.1, will it keep the mod?

2)If not, can I hardware mod the PW3 after updating it to 5.11.1.1? In other words, is it possible to hardware mod the PW3 on 5.11.1.1?