Proflex tape

That's not the Pro Flex 2 strips that I use on the seamless wefts.  The kind I get comes in rolls where the tape is only 1/4" wide.  That's the perfect width to fit nicely on the seamless.  I just cut the pieces off the tape roll to whatever length I need.

Since you already bought these, you could probably cut them to the right size and shape.  I don't know where you can buy the kind in the roll, since I buy them from my hair piece supplier.

No!

Where did you buy it from?

I put the proflex 2 on the back of each seamless weft and then also add hair piece adhesive for extra holding power.  You sandwich your hair between the pieces.