Elk -
It sounds like you've done your homework. I use the K-9 Cruiser attachment IF I'm going to the paved trail and nothing if we go mountain biking. My Weimaraner has her RN, CD, and 2/3rds CDX along with her CGC, JH, NSD, and NRD so her obed isn't an issue (and sounds like it won't be for you either). Us Weimaraner people frequently "road" our dogs especially getting them ready for hunting season. I'm also an AKC hunt test and field trial judge.
I have to put a plug out ther for the K9 Cruiser. I had both of my Weims hooked to the K9 Cruiser a couple of years ago and a squirrel darted out in front of us. The squirrel cocaine was too much for my well behaved obed/hunting titled dogs and they collectively tried to go in the direction of the squirrel. With the K9 Cruiser's low center of gravity, all that happened was the dogs managed to move my rear wheel a few inches to the right as there was enough forward momentum to correct the behavior without crashing me! The bike NEVER started to lean or tilt. I was so impressed.
Robin's road speeds easily reach 18mph (I didn't have her attached as it was a crappy day and no one was on the 8 mile paved loop) but like you said, I prefered to just run her at a trot. Just last weekend, she did about 15 miles on the mountain bike trails and the girl will be celebrating her tenth birthday in three months!
Be careful running, troting, or pacing on hard surfaces at first until she toughens up her pads. Teach her to drink out of your water bottle or a camelbak as it's easier than carrying extra water just for him/her. Everything else you probably know.
BIKE STUFF -
I accidentally woke the BF typing in bed

(he's still sleeping as it's 6:30 am on a Sunday) and he wanted to know who I was writing. I told him about your issues on the bike and as a Trek dealer himself, he said the 7000 would more than likely be fine once you find the right saddle.