How about angle iron instead of lift eyes? A piece of 1-1/2 X 1/4 L would do. Drill, mill, grind a hole big enough to take a strap or chain hook on one side and directly across dril the 6mm hole and then just bolt it. You can use a washer or two between the L and machine for spacing if you need too. I You can grind or cut away on the 6mm side to get clearance if needed. have never used a lift eye. I just don't have any. I would have to order them and good ones are expensive. I have plenty of angle hookups as described. I usually use a 5/16" or 3/8" bolt to pick up transmissions, engines, even truck bodies and frames. Just make sure the bolt is tight so there is no way it can bend. If you can upgrade to 8mm you will feel better about the whole thing.