I have ~ 0 experience of twins (grand total of 1.5hrs ME instruction
) but it's obvious that Piper recycle everything.
Isn't a Seneca a Saratoga hull, with an extra engine, and the wings longer to compensate for the wing length lost by screwing the engine partway up it?
The IMHO ghastly looking "Piperjet" is a Malibu with a jet engine screwed partway up the vertical stabiliser.
The Matrix is a Malibu with the cabin bleed valves removed.
And the PA28 family??
Keeps the tooling costs down, for sure.