well mismatched wheels is a wonderful turnoff for theives. There's nothing really wrong with having a 27" and a 700C...all kinds of bikes over the years have used different sized wheels.
You just gotta be ok with having to buy 2 different size tires, which doesnt really seem like a big deal.
That bar position is pretty far out. Most folks rotate em down quite a bit.
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--Don't Panic.