( I could not really call it an art.)

Now, there are always comments cropping up in AARs, Progression threads, and tactic advice in general, about people using numerous spies to cause a settlement to revolt.

I have an Arverni game in progress, which I will update in the FP thread, and it is at 252 BC.
I have conquered all of Gaul excepting the Aquitani and Nervii, and those hapless, fun-loving Romans are at it again!

It has been an arms-race since I conquered the Aedui in 271, (No cheating - I am having my best campaign in all the TW games I have played - all thanks to The EBBS Script Speed modification)

Both Romans and Arverni have gathered as many settlements as possible, and now I come to the point:

My main tactic, whilst war was undeclared, was to attempt to have rebellions caused throughout Italy.
I trained 20 spies, and sent 5 against Taras - it was converted to the Epirotes within two turns.
However, has anyone noticed that with settlements with no previous faction to revert to - no matter how many spies are in the town - the town will begin to rebel, and then suddenly go from 25% PO to 180%?!

How do you fix this?

I had Roma rebelling with 6 spies, and everytime it just flips back to 175%!

Please tell me how to wage this silent war!

Or is it impossible in this circumstance?

I can't even make Bononia or Segesta rebel.. Gar! Incompetence!