The bushings pulling out of the ESB-4 has been a long standing problem, partly due to the angle of the body where they go in, but mainly (I think) because the solid wood block down the middle is very soft (probably Paulownia) and it just doesn't grip the splines well enough. If you've finished putting the finish on, I'd just epoxy the bushings into the body. The bushings aren't the longest bushings there are either. I started building one of these kits and found some extra long bushings (30mm IIRC). I had to drill the holes a bit deeper to match. I didn't finish the guitar as the bloke it was meant for b**gered off and so gave it to my friend JimC to finish. https://www.buildyourownguitar.com.a...highlight=JimC

But I did buy a Hipshot bridge to replace the kit one, which isn't the best bridge in the world. That doesn't solve the bushing problem on its own, but it does make for a more solid string anchor.

With the kit bridge, you're best getting the bridge sitting parallel to the strings rather than to the body, as this reduces the upward force slightly on the two rear screws, so more of the force is forwards rather than upwards.