Well it was a sunny day, with quite full on wind but I managed to do a range test at last.
Rode along portions of the Eastlink bike trail:
and the Dandenong creek bike trail to the sea at Carrum:
The the last few kilometres I think I had reduced power though it was hard to tell with the headwinds I was pedalling into, but at pretty much exactly 50 km the battery flattened to the level there was no power to the wheel. So even riding in quite demanding conditions (sometimes the winds were really buffeting the bike so I had to work hard to stay balanced), it met the advertised range.
Interestingly a full recharge of the battery only used 6.44 cents of electricity (i.e. 0.3 kwH).. all in all very happy with the range.