I believe in everything stretches, however minute that may be.
That definitely was a ticking time bomb, especially for an interference engine. That's half a tooth at the cam. It's amazing how much these variable cam timing (VCT) engines can adjust for with no noticeable loss in performance...
Myself I won't go belt drive to replace pinion and spur gears. Knowing how much extra heat they introduce in a motor I recommend not to. I'd rather stick with the more common Pinion/Spur gear setups.
But if you want to try it, it's certainly up to you.
I wouldn't go belt drive. They create so much extra heat in the motor, are inefficient, and put excessive side loads on parts that aren't meant too. If they were such a great idea you would be seeing RC manufacturers using them as an OEM part.
The only good thing I can say about them is that...