To answer your question, it is not necessary to use the Dicor Lap Sealant along the edge of the Di-Seal Tape. That being said, if you still decided to do so, you should use a small bead because using a large bead of the Lap Sealant would pull the Di-Seal Tape from your roof.
I hope this answers your question! If you have any other concerns, please feel free to call our customer service at 574-264-2699!
Safe and happy travels!