"Regarding the 70 Mpix image not loading, I assume you are using the camera’s ASCOM Camera driver? There are some VERY inefficient ASCOM drivers that require over 1 GB of ram for a 40 mpixel image. The maximum memory for APPM is 1GB so the image fails to load. If the manufacturers would create efficient ASCOM camera drivers then APPM would not have a problem. Binning or using a subframe will reduce memory size below 1GB and thus APPM can use the image."
You are correct. As far as I know, APPM can only use ASCOM drivers to connect a camera. However, for me, point is moot, since I crop and get a smaller size file that APPM solves well! The addition of ASTAP is a great time-saver for model builds.