A good repair tape I have used for mending torn roll edges is Lineco
Mending Tissue.  When installed, it's practically invisible.  It is
pH-neutral and is used by archivists.  (Previously mentioned on MMD).

I'm not sure how good Scotch Magic tape is, but we all know that
cellophane tape previously applied to roll repairs has a limited
life -- it goes brown, dries out and falls off in time.  It would be
interesting to hear from a paper archivist what he or she thinks of
Scotch Magic tape for this purpose.

Geoff Ward