I'm sure you already thought of this spitz, but make sure to weigh everything, one of the good marketing points for yours will be if lighter or very close to the weight of the zcar one.
What do you plan on using for cover bolts through this plate? Bolts will be in double shear which if i remember my engineering school at all, is preferable.
However, I still don't see how this will stay sealed. The first blast off the line won't the bead of RTV touching the smooth surface of the sandwiched plate just tear apart - allowing fluid to leak through (granted it won't be a lot because it shouldnt be under any major pressure ever, but still will leak? Or am I just overthinking it and RTV will be able to handle the stretch)
And my apologies again, but did you already show your plans for the front mount? For this plate to work, the front mount will have to be bullet proof, correct?