OK, here is the requested information.
Antenna: It's a big directional NTSC Terk. I build a DIY 4-bay bowtie as part of my debug process and the Terk gets slightly better reception.
Orignal reception debug thread: http://www.avsforum.com/t/1435211/hillsboro-or-antenna-woes-time-for-a-roof-mount
TV Fool report: http://www.tvfool.com/?option=com_wrapper&Itemid=29&q=id%3D2df920a4389ccf
Are you actually in Portland or a outer suburb? - Outer suburb (Hillsboro)
Have you checked your local reception thread for local reception issues? - Yes. I had previously done a ton of debug (in another thread) and finally determined that the very dense apple tree & another house outside of the attic was blocking the signals. The peak of my roof is 2+ stories above the ground (need a 40' ladder to get to the peak) and will clear these obstructions. Installation is going to be a huge pain so overkill at this point (in terms of the mount) will not be a problem.
How prone are you to lightning? - ground strikes are extremely rare in the valley (where I live)
How old is the house? - 1998
Why no rotor? - All the stations are broadcast from 2 towers that are 2 degrees apart.
How long is the downlead? Antenna will go to a powered splitter that resides ~75' away (coax run length). A ChannelMaster 7778 can be added but I've been told that it should not be necessary.
How many 'taps' (TV's, tuners, DVR's) will you need? - 4 taps are in use but all are after the powered splitter.
How about a tripod mount? (Done right, the roof will not leak.) If there are advantages to the tripod I'd consider it.
Chimney: the house doesn't have a chimney.
House picture: Sorry, I don't have any pics on me right now. Here's a picture of a home with similar eaves & roof pitch. The eave mount would definitely work from a "room to lag bolt it in" standpoint.
The edge of my roof is exposed 2x6s so no problems there. I can run the ground wire down the inside of the eave to a new ground rod. The signal coax would go into the attic and be routed to the splitter from that point. If I go with a preamp I would run power to the attic in this location.