This may be of interest to the OP
http://www.fcc.gov/guides/over-air-r...n-devices-rule
"Masts higher than 12 feet above the roofline may be subject to local permitting requirements for safety purposes."
Seems like the suggested 10' mast is within the letter of the law. I'd follow ADTech's advice to get the antenna well above your steel roof to avoid reception problems. I'd also contact my local safety enforcement agency for a friendly conversation in light of the FCC regulations.
Yes, it looks to me like the DB8e is two DB4e panels connected together. Supposedly the two panels aimed in different directions perform differently than a single DB4e pointed in one of the two directions, ie not quite as sensitive as a single panel pointed at a specific station. The most sensitive configuration is both panels pointed in the same direction.
Not an industry member, but I would guess that removing the reflectors from a DB8e would make it bidirectional the same way removing the reflector from a DB4e would, as long as both panels are pointed in the same direction. I would also guess that if you remove the reflectors and point the two panels in different directions, you could have trouble because you may create a signal multipath problem (phase incoherence between the two panels for a single station).