Everyone I've seen for that range is 1/8" alum. but I suppose you could use phenolic also. Usually placed under the lugs for crush resistance and to displace the load.

I use a different system. 1/2" square motor mounts and 3/8" square aluminium inserts that are drilled and tapped for the engine. They are removable so changing to different engine isn't all that hard. Works for me.

How do you secure the 3/8" aluminum inserts to the 1/2" wood mount ?

Allan,

I machine out the 1/2" wood for the 3/8" square block with the block sitting about 1/8" above the motor mount. Then I drill out the 1/2 motor mount and insert a carbon tube to prevent crushing. Then I usually make an 1/8" steel pad on the back of the mount that is tapped for 4-40 or 6-40 (depending on the screw size I'm using. Then bolt the block to the mount.

I lost all my pictures in a foolish error on a back a few months ago, but I think I have some pictures of the mounting system on my current PA. I'll check when I get home.

Sorry to take this off topic.

Today i did two different trials. On a Skyray with 35fp i made 1/8 aluminum pads, i could tell no difference, got good runs by adding foam behind the fuel tank and not squeezing it down so tight. Also used a venturi sized for the 25 and that seemed to smooth out the runs quite a bit. On my Twister with 46la i tried my neighbors advice and cut pads from a 5/32 thick piece of hard leather belting, still i could tell no difference. Again foam rubber behind the tank worked. Now i need to figure out a good tank mounting procedure with the foam besides using rubber bands and hooks. Next profile i do i may try the inboard tripler.