Scott, I have those mounts on almost all of my planes. They are well worth the extra cost. I drill and tap mine and use #8 socket head cap screws with a lock washer on top. I've never had one come loose and I don't use thread lock on them Just tighten them up really well.

One word of caution when seting them up. Put the socket head screws in the spools with the lock washer under it before positioning the engine. This is espically important for the screw behind the carb. That carb has the idle and high speed needles on the same side and the highspeed extends back further than any other part on the engine that lines up with the mount screws. My first use of them was on a Magnum 52 fs on my trainer. I came across an OS 52 and switched engines. Everything was exactly the same other than that one screw and I ended up countersinking that spool and using a Stainless flat head screw in place of the socket head. It worked out well. Also remmeber that there is some movement between the mounts and the screw heads, so leave a bit of additional clearance to prevent the carb from banging the mounting screw.

I have a 3D plane that I first put the Mag 52 on. Then I decided to change to a 70. I was able to mill a bit off each mount lug on the inside and was able to use the same firewall holes. Even milling the lugs, I still have plenty of meat for the #8 engine mount screws.

These mount have without a doubt saved me a lot of engine repair time. I bounced my trainer off the runway countless times. I was buying props by the dozen and going through them at the rate of a couple a day. The engine never gave me a problem even with all the whacks it took. I think the motor mounts went a long way in protecting it.

I've got a set of them now that were on a plane I piled in so hard that the engine was in five pieces including the crankcase broke in hald and the cylinder broke off. The mounts are waithing for a plane and are in fine shape.

Don