Syncing lights question

So as I'm looking for ways to remove user apps/drivers, I came up with as question.

I have my handy dandy Dimmer Sync app. All it does is make a slave dimmer follow the master dimmer - on/off/level.

Obviously I could do that with 2 RM rules - a rule for on/off, and a trigger for level. Any other way to do it with less rules/steps?

One thing that concerns me is that in my app, the slave gets set to the master level at turn on time (via set level, not on/off commands). So with mode based lighting if the master gets turned on at 25%, the slave will turn on at 25% - not previous % and then a change down to 25%.