sequence cropping for super-8 film files

I am not sure of the quality but I imagine it is better than VHS. If so you can try different scaling methods as seen in the video below at 6:30. If it is for a client ask them which method they prefer.

102% on a 720 X 486 may not make a noticable difference.

And if it does, Neat Video does a good job to help SD media:

https://www.neatvideo.com/

Usually you match source stuff  (what you shot ) with what you edit.

You might have other ideas and there's a link somewhere where you can make requests to the progammers and colorists who make these programs your dream land.

Depends on your settings in Preferences.

• If you have the scaling option set to "none", it simply puts the 486 clip on the sequence using the PAR (pixel aspect ratio) of the clip at 'normal' size. So on a 1080 sequence, the clip will come in (typically) in correct proportions but showing centered with a fair amount of black pixels around it.
• If you have scaling set to "set to framesize" it will bring in the clip at correct PAR and auto-zoom until the first 'border' of the clip is reached. If the clip's framesize ratios are the same as the sequence, as for FHD (1920x1080) clips placed on a UHD (3840x2160) sequence, the image will fill the frame. If not, one 'dimension' will have black bars. And the full pixel resolution data is available for any scaling you may choose to do.
• If you have scaling set to "scale to framesize" it will do the above ... except!!! ... it will have mathematically computed the new image at the sequence frame-size, and any 'zoom' or image scale changes you make will be from the computed framesize, not the original pixels. If placing a UHD clip on an FHD sequence, this means ... that clip is scaled by Premere from 3840x2160 to 1920x1080. And if you then say "zoom in" by enlarging the image in scaling settings on the sequence, it recalculates the image from the 1920x1080 pixels up ... rather than using the original image. Which kills resolution of course.

You may note that neither of the above have anything to do with settings for PAR ... so there is always some user-choice involved. Are the pixels square, or not? Is the frame-size aspect width to height the same? Those are for the user to control.

Neil