Attaching corrugated polycarbonate roofing to soffit.

I’m trying to enclose an attached porch of a single family house. I have this corrugated polycarbonate roofing material to serve as the roof for the porch, and it ends right next to the house right under the soffit, with maybe 1-2 inches of clearance. The porch roof is on a slope of 12 run / 1 rise (I know this is really shallow).

The issue is during heavy wind, the roofing material under the soffit moves and hits the soffit. It is quite loud in the interior room next to the porch.

I’m wondering what is the best way to secure the roofing material to the soffit so there’s no loud noises during heavy wind. The portion of the roofing material under the soffit is not secured on purlins as I can’t drill fasteners in top down due to the soffit being in the way.