Thanks.

I am tending towards a Marathon Plus in 1.35" wide on the back as a 'set and forget' tyre. Puncture resistance is a big plus especially considering the IGH with coaster brake and that the rear tyre gets the most wear by far.

Interesting to hear the Big Apple may not be quite as wide in real life as the specs would indicate. A lighter and maybe wider tyre might make sense on the front. Less harsh maybe (although it is tempting to go for one of those ultralight foldable tyres in the front so as not to add too much weight to an already heavy bike.)?

Any opinions as to what might be considered as going just 'too narrow' on a 20" wheel, considering the odd muddy path and bumpy bike lane?