Go and purchase a small threaded bar from the DIY shop or a long bolt, 10mm or whatever, and some nuts to thread on.
Put nuts onto bar and screw them up until they are less than width of rear dropouts.
Insert bar between rear dropouts and screw nuts out towards dropouts until they are 'snug'. Measure and it will be 130mm.
Start screwing nuts to force frame out (splayed) and increase the spacing and keep going until you can't suffer the worry anymore.
Release the nuts and watching the frame 'Spring back' to 130mm!
Keep doing this, praying, sweating and worrying until you splay the frame enough to create permanent deformation of the frame and you get the spacing you desire.
An old 531 frame I had was splayed out to 195mm in order to take it from a spacing of 125mm to achieve something like 128mm to enable me to fit a 130mm spaced axle. I was very nervous and sweating about doing that!
At least with the threaded bar and nuts it is more refined than just putting your foot on one chai stay and pulling the other. You can also move each bolt if you think that feels better!