Flow and return from solid fuel stove

[david60]

Hi,
My question is about the flow and return in a primary circuit from a multifuel back boiler in a gravity system connected to an indirect cylinder. As I understand it,the run should not exceed six meters. My proposed installation does exceed this distance and I would like advise on how to remedy this safely.
Is the length measured from the cylinder or the heat sink rad?
The flow and return pipes do rise vertically to the ceiling, thereafter it will be necessary to have horizontal pipe run to the rad and cylinder.
Thanking you in anticipation. David