Since you have "chewed up" the wood a bit in the area where the spikes should bite, try filing the points a bit sharper using a Dremel cut off wheel or flat file (Dremel is much easier). If you shorten the spikes a little it won't matter, they just need to hold enough to get the engine on and the bolts in and tight. If you can get your finger in where they are, you can dob a bit of epoxy on the edge to hold it after they are seated. That must be some kind of hard wood, or the blind nuts are very dull. If that doesn't work, ........?