I think the gun on the reavers can turn, and also how would a galaxy ram a reaver or a mosquito? The galaxy is too slow. Unless the reaver or mosquito pilot is hovering or going really really really slow, the galaxy shouldn't get a chance to ram it, and even if it did, i don't think it would just blow up in one hit. plus i think the turrets on the galaxy only move 180 on the x axis, and any 3 mosquitos can take it out in 30 seconds if they know how to fly and attack well. also, the galaxy probably couldn't land on any troops without them noticing so they will have time to run.
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