How to achieve a flawless fit for an oversized arch window? For this 130″ by 200″ arch window, it was no easy feat to create the an inside mount with no light gaps. The secret to our success: leave the returns (ends of the frame) and the bottom gatherings unfinished before mounting on the wall. This leaves ample room to alter on site to arrive at a perfect fit.
Also, use 1/2″ or thicker cording to seal any light gaps.

Dao Zhou

Drapery Designs