Originally Posted by Homebrew01

Are those ordinary playing cards ? I have found that those tend to fatigue rather quickly and cannot handle a lot of cycles. Additionally, they are suseptible to the elements which can further reduce effective usefulness.

I suggest using a 100 % synthetic card of a more resilient plastic that will give you many more miles of use before needing replacement.

Also, the attachment pictured appears to be celophane tape based, which I don't think is sturdy enough for long term use. A more rigid clamp will last longer and keep that card properly placed for optimal performance. The type of clamp will depend on the type/size of seatstay.