Like Brendan said, acetone is evil stuff for acrylic or lexan. I have used it to clean gel coat on both my sailplane and my boat. As he clearly states, it will soften the finish and should be used carefully. I am on the other side of the US from TAP so I cut my own windows. It is not that hard. I prefer acrylic over polycarbonate, it lasts longer for me. To seal the windows I used marine grade butyl tape, you can optionally embed a spacer in the tape to avoid too much squeeze out. The spacer is a plastic line like string trimmer cord. Commercial window dealers sell the butyl tape with the spacer. No leaks after 6 years in hot wet Florida.

imo avoid silicone unless you get the best commercial quality. Your local hardware or West Marine do not sell them. Very hard to use for a first time repair. mariner #44

:: Where can I find how to repair Express Window water
:: leak?

:: I heard it is common for Express 27. Any article or
:: instruction for the repair?