Currently installing the piping for my central heating system. I planned to do the backbone in 22mm copper and run this the length of the house down the centre of the 1st floor (roughly 10.5m) front to back. These 22mm pipes will be fed from a Wb greenstar 34cdi combi which will tee into the 10.5m stretch in the centre of the run. I then planned to feed each radiator from the flow and return backbone in 15mm. All of the radiators on the ground floor will be fed from drops so the 15mm pipes for the furthest ones will have to travel roughly 3m horizontally and 1.9m vertically for each. There will be 6 radiators on the 1st floor and 7 downstairs. Will this be okay or should I try and take the 22mm backbone closer to each wall in the upstairs rooms? The notches for the 22mm are already cut down the centre but I could alter if needed.