If this is the type of engine you're referring to, I use the pictured tool to unscrew it. It's a DSLR lens bezel removal tool. It can adjust to different widths and the sharp end fits in the holes just fine. The engine is snug, but not a problem to remove.I would also really appreciate recommendations on the best tools for the job particularly for unscrewing the entire light engine. The narrow needle nose I have might work but I know it's not ideal. I imagine something like a 90° bent needle nose perhaps. I just want the best tool for the job so as not to risk any damage, which would be heartbreaking. If any of you could please recommend an exact make and model of tool it would be great!