Turn around and use your house as a backstop for your backstop.
If you’re not comfortable enough with a random stray arrow flying into your house, you shouldn’t let one go across the privacy fence either.
Hang the 8x8 near back of house. Put an appliance box full of rags and old clothes from Goodwill (bought by the pound) in front of that. You will never shoot through the box, and hopefully won’t miss it.
Happy shooting.