To answer in no particular order:
If she's in a crate, she has to be on the floor. Her crate is a standard 42", which barely fits her.
Mostly she has been in the back. The back row is fold flat and her crate is on top of those. But last night I tumbled the front seats and put her almost directly behind the passenger seat. She still panted and leaned forward against the front of it like she wanted out.
We really wanted her to be crated so that she can't see because part of the problem with the Civic is her absolute belief that bicyclists and people who aren't walking properly (whatever she decides that to be) and, of course, dog walkers are Evil Incarnate and that she must sound the alarm and throw herself against the windows.

It's okay when there are two of us; we scan the road and tell her to lie down if we spot the evil before she does. If there's just one of us with her, it can be almost dangerous how startling and loud she can be while you're driving. Plus, it can get a little tiring to be constantly scanning the horizon on a long road trip.
She can't really stretch her neck up in her crate, she has to stand with it ducked like she's in a room too short for her.
What sort of homeopathics are recommended? Or does ginger work? If she'll eat it.
I like the idea of a platform anyway, and maybe that could work if it is a looking outside thing.
I'm open to the idea of basically building a pen in the "back-back" but DH really worries about her being loose in the car if she's left in it (part of what we wanted to do was be able to take her with us everywhere for the nine months of the year we have no sun) because of her reactivity issues.
Thanks for the feedback, though! If anyone else has other thoughts, I'm still all ears!