To prevent your engine mount screws from pulling through the chassis aluminum from vibration (first pic), add some large diameter washers under the heads of the screws (second pic). This spreads the stress over a larger area. I used zinc plated washers from McMaster Carr item # 91100A120 3.2mm ID 9mm OD $1.07 for 100 (plus shipping). You could use a bigger washer and grind the edges if necessary to get them to fit in the recessed area of the chassis.