Not an excuse. See
http://www.fcc.gov/guides/over-air-r...n-devices-rule
Repaired TVFool plot link:
http://www.tvfool.com/?option=com_wr...d243e32f8a0950
Expecting to get WTTG and WRC with an attic-placed antenna is probably an unreasonable expectation, but it depends much on the attenuation of the building materials and also what's outside - trees, buildings, and the like, in the signal path.
Best bet would be a directional, high-gain UHF antenna if you're focusing specifically on those two stations. You'll likely get most, if not all, of your Baltimore locals off the back of just about anything, again dependent on the attenuation variables already mentioned.