I'm running a 120 mm track hub in a 126 mm spaced frame. Like Sam says, get some spacers and use them to align the wheel. As you've already identified, you'll need 3 mm either side to get the chainline right.
@andyp started
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I'm running a 120 mm track hub in a 126 mm spaced frame. Like Sam says, get some spacers and use them to align the wheel. As you've already identified, you'll need 3 mm either side to get the chainline right.