Stupidly didn’t do the proper research and told my builder to set out my skylight opening at 2.3 m by 1.3 m, standard size is 2.5 m by 1.5 m for the internal opening, Can I get away with this? Or get my carpenter back to alter the internals? The difference in price between the two sizes with the size I have being custom is over £700 so not really worth it. As the carpenter assumed I was having a lantern there is no fall currently so I have some furring strips to add and then need to osb and get the flat roofer back to finish off sealing the roof anyway, any advice on this would be appreciated. It appears that most suppliers offer an internal frame for the fitter to fix too I didn’t know if this would change anything.