Using Polarizing Sheets

Hi everyone! Looking for some advice. I am shooting photos of framed artwork in a gallery and studio space. I use a polarizing filter on my camera lens, as well as a polarizing sheet over my light/softbox. I've only been able to find rolls of Polarizing sheets in 17" wide strips. My softbox is a bit wider, and when I lay my polarizing sheets over it there is a seam. I'm wondering if anyone has found any solutions to the seam? The best I have found is laying another smaller strip of polarizng film over the seam and securing it with black gaf tape (photo in comments for reference). I'm sure there's a better solution, any ideas?