If you had been flying RC back in those days you would have had a problem with the relays both in the tube rcvr and the rubber band escapements...both very sensetive to vibrations. That is where I became an advocate of BALANCE.
Your comments re engines being inherently 'out of balance'... I would agree but engine mfgrs make a real effort to balance by applying a Bob weight to the crank pin (usually 1/2 of the weight of the reciprocating weight: connecting rod, wrist pin and piston assy). The crankshaft with this bob weight attached is then dynamically balanced electronically to .03 oz inches. Thes figures vary with mfgr. Glen