How do you meet the IVA requirement for a fuel tank vent, below? I've got a non-return valve to cover a dropping level but this will not do anything for vapour pressure build up on a hot day.

Do I need to worry about vapour pressure? Any IVA friendly solutions?

IVA requirement; "The fuel tank must be fitted with a vent (to permit release of a pressure build up) which does not exit on to the exhaust or into the vehicle or be situated at such a height that fuel would be likely to leak when the vehicle is driven."

Some fuel caps are vented or have a vent pipe in the body of the unit. The easiest solution is to use one of those.

I've done mine in a piece of fuel hose looped upwards and then back down to just below the level of the floor

^^ same here, passed SVA OK

Hi

Short piece of hose and one way vent valve off a MotoX bike.

Used a vented fuel cap...