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Sure, but timing (from my experience with engine tuning) tends to be worth only a few percent - maybe 5% tops, unless it's very drastically off (tens of degrees). Most engine programs have slightly conservative ignition timing. Propane's flame speed is nearly the same as gasoline's, around 7% faster, which means if an engine computer's timing is slightly conservative for gasoline, it ought to be just right for propane.
Both gasoline vapor and propane vapor burn, rather than explode. If they explode, you have knock, and it tends to damage things. Propane is actually slightly more resistant to exploding.
In terms of ignition timing, at low RPM high load, the ignition timing in my K24 engine was very nearly 0 degrees. I needed to back it away from zero on lower octane fuels, but under ~1250rpm the ignition event was set within a degree or two from zero - because for best mechanical efficiency, you want peak pressure to build up by ~15° or so, where the piston is not just pushing straight down onto a vertical crankshaft. So, the angular time until peak combustion pressure (when a majority of the fuel had burned) was approximately 15 degrees of rotation.
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