Hi and welcome back! On the PAC SU-26. Is the plane for a 40 size engine? If it is and I assume that the mounting blocks are made of hardwood, I would rethread the mounting blocks to 10-32 size and then coat the threads with CA to toughen them up. Then use nylon bolts from the hobby shop. Reason being, I found out that metel bolts can loosen themselves off from vibration during flight. Nylon bolts are vibration resistant and won't loosen on you. Wings bolts coming loose are a bad thing! [X(]