Greeting to you in Indonesia! You can't get much further away than half way around the world.
The wood engine mount I made myself with hand power tools. As you mentioned, the engine seated too low against the pedal chain guard with the stock mounts. Not to mention the rear clamp is at the wrong angle for most bikes and fits like crap. Taking the time to make a wood mount was more an act of desperation. The side benefits were the integrated muffler mount and the elimination of the chain tensioner since the engine assembly is adjustable forward-back. The wood rod along the down tube is oak. Spruce would be too flexible. The angle of the wood rod is set to keep the carburetor level. The plywood on the sprocket side of the engine is 1/2" maple sold at Menards. The upper rear screw under the buckbar lever extends into the plywood. The plywood on the clutch side is 1/2" 4 ply pine and is held to the engine by (2) 10-24 bolts and tee nuts using the existing screw holes holding on the clutch cover. The factory rear mounting system is not used. Under the motor is a V shaped piece of pine that maintains the orientation of the engine when the screws are loose during chain adjustment. There is a couple of fancy mill cuts and some shimming to match the downtube, the diameter of the seat post, and clearance at the drive sprocket housing . The subframe is extended in the back to add bolts to clamp the frame and to reverse the pull of a clamp so as the clamp is tightened, the engine moves forward to adjust the chain. For safety in the event the wood rod would break, the muffler support would prevent the motor from being pulled to the left by the chain. In addition, there is a safety strap bolted to the engine that loosely wraps around the downtube. I would not mind making a batch of mounts and selling them; but I have not found a comfortable, affordable way of dealing with liability issues.
The rear engine mount is replaced by three existing screws; but since the load pulls the engine into the mount, it seems to be adequate.
I should go on to add that the wrist pin has been replaced with a lighter titanium pin from Juice Motor Supply; reducing vibration from a stock motor. With this motor build, I could ride all day without vibration related fatigue letting the wood mount absorb much of the remaining vibration.
Up until recently, the fastest this all steel bike would go is about 24 mph. With the iridium plug and the NT throttle cable sheath taped where it meets the carb, I'm going 30 mph. This makes a difference as to how often I am willing to take the lane going through town; increasing the usefulness of the bike. The added utility makes the wood subframe worth the investment and also more needed since now the engine is running at higher rpms.
