Okay, so I've done a bit of digging, and it appears that the Canadian Trimotor was fitted with
Brewster floats.
From 'Ford Tri-Motor, 1926-1992', William Larkins.
'6-AT-1 was built as a seaplane and was licensed by the
Department of Commerce under Memo 2-80. It was first
flown on May 14, 1929, purchased by the Royal Canadian
Air Force for $92,650 and delivered in June as G-CYWZ.
At that time Canadian government airplane, including
military aircraft, carried a civil registration in the early
Canadian series G (Great Britain) - C (Canada). Only the
last two letters were painted on the RCAF plane, however,
and thus the Ford was known as "Old WZ."
It was initially used by the Civil Government Air
Operations Division for experiments in forest dusting, and
for this purpose operated from rivers and lake on large
twin Brewster floats.
The first of several Ford Tri-Motors to be modified with
tanks for agricultural use was 6-AT-I in June 1929.
Although "WZ" (short for G-CYWZ) was owned by the
Royal Canadian Air Force it was used by the Civil
Government Air Operations Division for experiments in
forest dusting. For this purpose it was operated on
Brewsterfloats from lakes and rivers. Operations stared on June 17,
1929, on the shore of Duchibany Lake in Canada.'
cheers,
Robin.