never mod on 1200 yet but did work on P180 and others.
You have two options
- do two windows; just remove the stock gill mesh and replace it with acrylic
- one uniwindow
since stock window is bolted on so you have to do bolt on style but this will be a little more work and harder, second you much have Die&Tap tools to thread the acrylic. I think it's best to use two sided tape, 3M type. You can find all the materials at HomeDepot, you should get the acrylic sheet at least 1/8" thick for stability.
Anyway here are the links for you.
Worklog link
Video log
Enjoy!