Something easy to miss about the original design: the gate, the mask that frames each visible frame, isn’t part of the viewer at all. It lives in the cartridge itself, one per cartridge, not a fixed opening in the mechanism.
The Fisher-Price gate itself is genuinely accurate to the real Super 8mm spec, not just close enough. Still, it leaves a clean, tightly bounded frame, and there’s usually more actually exposed on the film than that frame shows: a camera’s own gate exposes a bit more image area than the standard viewing frame reveals, on Fisher-Price cassettes and on a normal cassette alike. That extra image is sitting right there on the film. The tight gate just never shows it.
That’s what makes an overscan option genuinely worth having, not as slack for tolerance, but as a way to reveal everything the camera actually captured: no secrets, the full exposed frame rather than the cropped one. Even then, it’s not a free-for-all: showing more still means deciding where the new edge actually sits, so the mind still has to frame it, just with a wider frame to work inside of. Since the gate belongs to the cartridge and not the viewer, this could realistically ship as a real option: tight frames as the clean default, overscan for anyone who wants to see everything the camera actually caught.