I had a few hours this morning so i decided to work on the loft and added all of the collar ties. This give us space to add lights and also to add insulation which wont come into contact with the roof membrane. I measured the 2 ends and also the middle one and then ran a string line between them all and used a level to make sure everything was straight. I tried 2 sheets of insulation in the roof to see how it fit and i think its going to work well.