There are probally other sites that have this also.

Here is a link that might be useful: poly. film tape

Personally i`d opt for a mechanical fixing rather than using tape. Any weight on the sloping section of poly will likely cause it to pull away from the tape.

I wouldn't trust anything like tape, especially at the peak. Too hard to fix in the middle of the winter, which would be when you'd have a problem--at the most inconvenient time!

I recommend you to import some PE film form abroad, maybe it can help you save money.

Here is a link that might be useful: PE film

This Poly Patching tape has worked well for me, although I have not subjected it to shear stress. Just for patches and a few joins. Laughs at the weather. Never comes unstuck. (scroll down about mid-page at the link below).

Here is a link that might be useful: Poly Patching Tape

You'll find few endorsements for the poly patching tape other than to cover a puncture hole here and there. As stated previously a mechanical fix is preferred such as a wire-lock base. I've ordered narrower plastic sheets and had seperate sheets for roll-up sides. The problem of piecing together at the peak is that you would need a bucket truck to fasten the overlapping sheet unless you bunch it together and install- then you have the issue of unbunching which is more of a problem than just pulling the film in place.

Plastic film isn't exactly cheap but neither is the tape if you need to use a lot. Another joining method is to purchase a heat sealing unit; also not cheap and awkward to use. If your ultimate goal is to save money than buy a full sheet of 6 mil GH film at least between hip boards. Then do as I do and don't replace it for 10 years or more.