When is it OK to make a compound noun solid?

My spell-check balked at "bootprint," which I thought an obvious corollary to "footprint."
That is, if a bare foot leaves a footprint, a booted foot obviously leaves a bootprint.
Alas, three dictionaries have failed to back me up on this, although NASA does, referring to its image of the print left by Buzz Aldrin's boot as a "bootprint."
What do you think? Can I close up this compound, or should I keep it open?
Kristen,
I think you can do whatever you want--just be firm in your convictions.
My conviction is that my spell checker is pretty stupid.
Emmett

Ditto on spelling and grammar checkers.
My favorite counter-example was when a spelling and gammar checker, which will go nameless, but is associated with a giant software company and one of the richest men in the word, insisted that "doing good for all people" should be "doing well for all people."
I try to live by the "doing good" philosophy, but others, it is very clear, are committed to the "doing well" philosophy.

Alas, three dictionaries have failed to back me up on this, although NASA does
You go girl! Sometimes you gotta push beyond the stodgy envelope of dictionaries and be a part of language evolution. But keep in mind that you can't always count on NASA as a reliable language reference. After all, they are the ones who gave us "that's one small step for man; one giant leap for mankind."
There must be a lot of bootprints in boot camps.

I heard Armstrong live, and it always bothered me when folks changed his words to include the "a." Clearly the statement with the "a" shows greater rhetorical structure (OK. Without the "a" it makes almost no sense.). Recently I stumbled on the transcript from NASA with its discussion of this very topic:
NASA transcript
I feel much better now.