Usually people woud go the other way around, starting with long acting and going to short and then adding in the fat burners toward the end. But if you wanted to do this, you should be fine to continue running the short esters for an additional week or so after the long esters are started. You will have some hormonal dip still. Honestly thre is no way to avoid it to an extent. You either dip down a little or leave the short ester in and levels get higher for a short time, only to drop back down