For the past few months, I've had nothing but continuous problems using these mounts. First I find them very troublesome to even drill accurately. I'm open to suggestions here. I've also experienced sever vibrations to the point the plane won't fly due to all the vibes going into the plane. This has been with Tee Dee's , Norvel's etc. These are all mounted on combat foamies. I have a double 1/8th lite ply firewall that is glass reinforced. The mounts also break right at the rear mounting bolt holes. I mic and drill the holes for a 2-56 screw. I then took a drill bit that was ground to resemble a brad point drill bit made for wood. The point centers the bit on the exit side of the hole and cuts a flat on the exit side of the hole so the nut is sitting on a flat. The past 4 that I did this way all broke and vibrated badly. Should I be using a self tapping screw to go into the composite rather than a machine screw? I've done this on similar mounts on .15 size planes using a allen sheet metal screw that Dubro provides and it worked well. Although, it does screw into the hole rather easy and you have to constantly keep the screws snug. It also bulges the sides of the mount probably due to the screws being close to the edge. I'm not a fan of this but like I said it works. The only way I drill these is clamped to a ground block. There must be an easier and more accurate way of doing this. Looking on the net I've come across Fourmost mounts which show a Tee Dee installed in it. The mount cradles the engine rather than have it out onto two  beams. It looks quite heavy. Anyone use one of these mounts? I recently fabricated a aluminum mount using 6061 t-6 using the same bolt pattern as the Dave Brown and braking triangulated gussets into it. The mount worked great until it cracked in the corners. I guess it worked hardened and the vibrations did the rest resulting into poor runs once again. Ken

I have never had a problem with the mounts.  I don't use the sheet metal screws as I think they stress the material.   I drill and tap the material like I would metal mounts.   

                I was drilling a hole for a 2-56 screw. Without thinking off the top of my head I'm going to say I probably used a 3/32 drill bit. I never thought of drilling and tapping the plastic mount. It would be obvious the smaller I make the hole the better off it would be. I could grab the engine with my hand and with minimal effort break it right off the ring. I couldn't believe it. I did this twice, so I surely don't think it is a manufacturing flaw. I'm certain the problem is on my end. Ken

I use Tatone metal mounts. Drilled and tapped for 2/56 threads. I have used the Dave Brown mounts and they are hard to drill straight.  I know Tatone mounts are hard to find and I allways keep looking.  RC swap meets you never know what you will run into. Found a Tatone mount for Space Hopper Cox .049. Very rare as this is a long mount for rear induction engine.