Doug,
I have always used 800 kg (1760 lbs) as the weight of A89’s trailer, which is a 1975 Bramber trailer, converted to AOA spec by Zetwins in 1977.
I’ve just been online and basic modern 26 foot trailers are quoted as 670 kg – 750 kg, so when you add the weight of the 3 timber supports, it adds up to about 800 kg.
Richard