Combined shipping is fine. The Shipping cost is per shipping tube. Usually I can get up to four posters in a tube. Buy what you would like. When done request an invoice and on the invoice I will adjust the shipping cost down.
I most always Ship in a day or two. However please note that in order to accommodate combined shipping I have set the handling time to 15 days. Just makes it easier for those who want me to keep a tube open for them although you who combine will not be limited to 15 days.
Also note shipping is running slower these days. Just the way the world is. Neither sellers or EBAY can do anything about it. We have tried.
Stay Safe ......