Originally Posted by dddd

I've spread a few 120mm frames out to 130mm, so as long as you have controlled leverage and can bend each side separately while measuring each side's 5mm movement, this is quite do-able.

This frame is a track bike?

Also, to help the stay's resist coming out of alignment while riding, it's best to bend each stay 6mm, then back 1mm. You'll see that it takes quite minimal force to bend back that 1mm, which is merely a stress-relieving process that helps the widened frame hold it's "adjustments" better later under riding stress.