Your new mounts look great, Chris. It would seem that there are two or three questions that will determine your decision as to whether or not do them in brass: 1) will the plate be more in scale if it is (~.016" thick if 1/4" in 1:1); 2) if done in brass, what does that do to affect the scale of your motor mounts as compared to all the plates you've made, which I'm sure is .016"; 3) how much work will it be to have brass ones turn as out as nicely as your styrene ones? Whatever you choose to do, I know it'll be the right choice.