Another approach I have used is to pop out the blind nuts and then drill out the current mounting holes to the next convenient birch dowel size. then Using CA or epoxy, fasten the dowels to the drilled holes. Flush the dowels to the top mounting surface and then drill for the new mounting configuration. If you can't get to the underside of the rails to secure blind nuts to the new holes, get some "Nutserts from TruValue and insert them into holes sized appropriately. Nutserts screw into an oversize hole in wood to give you new metal screw threads. Kinda like Helicoils, but for wood and no need to pre-tap the hole for the Nutsert. Works for me.

Sincerely,. Richard