Delta, I am looking forward to hearing what you've discovered.
3M Scotch frosty tape will probably hold longer than the original splice!
I've used it on cassettes and reels since the early 80s and no problems!
Old-style splice tape is not as flexible as the newer tape, and the adhesive is less likely to migrate out and stick together adjacent layers on the reel.
Many times the failure in playing is because the plastic backing of the splice tape is not flexible enough and it pops off, while if it had been less
stiff, the original adhesive may have held.