Will singletons and granted construction permits be allowed to file major modifications in the settlement window?

No. Major modifications will be limited to stations identified as MX on the public notice announcing the window. Major mods will only be for the purpose of resolving mutual exclusivity. Applicants wishing to make major modifications must wait for another filing window (which will likely be several years from now). Please note that if the reason why you need to make a major modification is because of interference you are receiving (or giving), you can request a channel change to any channel (not just the adjacent ones) upon a showing of reduced interference. You can't make a physical site move more than what is allowed as a minor move.  Please contact REC (1-844-REC-LPFM) for assistance.