A lot of the older derailleurs, like Suntour Vx/Cyclone, were designed to work with either an integrated derailleur hanger or with a "claw", which puts the derailleur a lot further out than an integrated hanger. So they needed some excess movement range to accommodate these mounting options. Many of these were well into the 126mm rear spacing era, only 4 mm narrower than this. I just measured the width of the "claw" on one bike. It is about 4.5 mm. It is a Suntour Vx medium cage running across a 6 speed 14/30 freewheel now, but I've had a 7 speed 13/28 on the same derailleur/wheel/bike, which is spaced at 126mm. This tells me it would work on a bike w/an integrated derailleur hanger w/130 mm spacing unless I'm really missing something here.

Probably the reason people are telling you it won't work is because of the indexing issues, which is true, these are not designed to work with indexed shifters. But in friction mode, a lot of these old derailleurs will work fine.