Hi Fiona,

As a seller my feedback rate is probably approx 80%. 

I send a message that I have posted, & that "if there are any problems, please contact me".

I then leave feedback for the buyer.  All finished my end.

I never ask for feedback.  Sometimes it appears weeks later.

I am certain they would contact you if there are not happy. 

You could perhaps write a blurb (re feedback etc) and put it in the parcel?