PB stage 2 rear basic bags

[swanga c10]

Hi
Im in the middle of installing the Porterbuilt stage 1 front and stage 2 rear basic kit to my 69 C10 and have just realised i didnt receive the cups for the rear bags. Do i have to run these cups? i have seen somewhere on here where someone has just mounted the top of the bag to the bottom of the c-notch, i just cant seem to find the thread again.

Any help would be greatly appreciated.

regards
JI