I was being a bit dense. 1/16" Interference fit gives me 1/4" & 5/16" hoses coming off the top of the tank, with as you say 5/8" for the Vent & 1 3/4" for the filler hose. The 1 3/4" is becoming difficult to get over here as it would seem that the manufacturers are making 1 1/2" & 2". I don't know how long the P30 Chassis was made for but I think it would be wise for anyone who hasn't replaced these hoses yet to consider getting them replaced over the winter. I was lucky in that I had LPG to fall back on. When it started leaking I switched over to Petrol & put my foot down to burn what was left in the tank as quickly as possible (which didn't take long!!!).