India Four Two,
You're a lucky man to have flown both - in truth I've never even seen a DHC-1B in the flesh (there's only one in Australia, an -S2, not airworthy and hidden away).
Just to clarify, the DHC-1A-2's supplied to India were fitted at the factory with undercarriage leg fairings, though they seem of lesser chord than the UK-fitted ones.
I certainly will take a tape measure to Omaka! From Hugh Shields, the guru on Canadian Chipmunks, comes the suggestion that ALL Canadian Chipmunks had the narrower cross-sectioned windscreen. DHC's remedy to criticisms of the restrictive narrow canopy was the superb blown one. This still seems a simpler and far more elegant solution than that produced by DH in the UK. Apparently the original Canadian blown canopy doesn't match the UK-style windscreen; now possibly I have the explanation.
Cheers.