Thanks all
Jesse, job is going to be done by aviation engineering shop and they’ve done them before – not DIY. Just making the point that working with plastic is not easy.
Here’s the LP Aero STC info :
The Original Design: Before 1973 or 1974, depending on the model, all Piper Cherokee, Cherokee Six, and Seneca series aircraft were equipped with 1/8" left and right windshields. Thereafter, Piper offered optional 1/4" windshields as part of what is known as the Super Sound Proof package.
The LP Aero Plastics, Inc. Mod: This STC provides a means to retrofit the later FAA-PMA optional 1/4" windshields on all of the earlier models. This is a basically straightforward installation, however the 1/4" windshields are a tighter fit and require a more precise trim. No modifications are required to be made to the airframe.
After 1973 or 1974, depending on the model, these aircraft were certified with either 1/8" standard or 1/4" optional windshields, which means that either thickness can be legally installed without an STC. On later aircraft, the only sure way to determine the installed thickness without removing the windshield is to check the aircraft equipment list for the installed option.
Competitive Information: No other company offers this type of STC modification.
Options Available: Clear, Green, or Solar Gray Tints are available.
