So, in the lowest position, there's a whole 18mm clearance between the rear mech cage and the ground! I'd need to keep that rear tyre fairly hard...
I've since removed a few links to pull the mech cage forward a bit, but there ain't much room there. This ok?
I found on the road it was very rare to actually hit the derailleur on the ground unless to hit the likes of the edge of a deep pothole just wrong as the wheel normally lifts the bottom of the cage away from danger.
Offroad it all depends on how big the stones you are cycling across are. Again I tend to steer to keep the derailleur away from the edges it can knock against. The other thing to work out is does a duplicated gear give you a better ground clearance and is it worth using. But what is much more common when offroad to fill the derailleur full of grass/twigs.
I'm another who used to run a big range, 48-36-22 & 9-32, on a full derailleur setup. It's important that you can use big-big because of the risk of damaging something if you cannot. But if the derailleur causes the chain to rub against itself in small-small it's no real problem. I just didn't use that combo unless I was tucking the chain up away from risk when offroad.
Now I just run a 55-38 double on a full hub gear setup.