Andrew R Stewart 

Many shops and basement wrenches have done similar gearing changes. My suggestion is to put on the lowest gearing you can, even at the cost of higher ratio ones.

At the rear I would suggest replacing the road spec der with a MtB one that matches the indexing cog count spec. IIRC the 9 speed Shimano MtB ders are cross compatible with 9 speed road shifters and cassettes, so a cassette with a 34T low cog can be used.

In front the 30T ring can be changed out to as little as a 24T. But the shifting starts to really degrade (assuming common/poor shifting skills), the gap to the 39T (or 42T) ring grows and cross chaining becomes more problematic. As front shifting is so very rider skill dependent some riders who exceed the spec ring range will have little problems dealing with shifting onto and off of that inner ring. But some riders (sometimes on rides I think this includes most of my riding partners...) have issues with front shifting the in spec/OEM front systems and these riders will really suffer with a huge front ring teeth count spread.

Are we to assume that the rest of the bike's design and features will handle the tour's load needs? How wide a tire can you fit? Andy