Is there a (free online) source for sectional charts, downloadable as an image file, that cover your choice of area boundaries, and are "seamless" across a boundary between the official FAA chart sections? My purpose is to view such an image in standard image-viewing software, on a PC (for planning) and on a smartphone (for reference during a flight).

E.g., our soaring area is near the border between the "New York" and "Montreal" sectionals. In the past I've downloaded both of those sectionals from the FAA web site, cropped to a smallish portion of each, and "glued" together manually in image editing software, trying to line up the longitude lines. That's tedious to do precisely. Also some map features (e.g., some roads or rivers) then still have a discontinuity where they cross the boundary, even as other nearby features cross smoothly. (I have no explanation for that.)

I think the CMR files can be joined seamlessly, but they are not suitable for direct viewing by human eyes, outside of specialized software that re-projects them. As is, the aspect ratio is distorted, e.g., circles look like ovals. Lynn has told me how to use such software to then export the reprojected seamless image, but the procedure is more of a hassle than I'd like to tackle.

There are several web sites where you can view sectionals in such a seamless way, but not download. (Screen image capture doesn't count, the resolution is too limited.]