I don't use inner covers with telescoping covers. I use migratory covers, made from plywood. The 3/4" hole can be front or back or both, don't matter, I myself chose front. It can be plugged with any 3/4" plug, be it plastic or cork or wood stick or duct tape. Bees will close it if they want but I've not had them do that yet, they seem to like them and use them. From what I've been seeing, I may just stop using a full open entrance and just use holes instead, the bees seem to really like them.