My bike with its custom dropout has the slot at 11 degrees, roughly half way between horizontal and perpendicular to the seatstay. (I actually used the brake position, not the seatstay.) I can run any cog between 12 and 24 teeth, keep the brake pad on the rim (cheating and using the Velocity Aero rims which are pretty deep) and the BB height doesn't suffer too much when I slide the wheel all the way back for the 12 tooth.

Andrew, I have an easy routine for mounting the rear wheel and dealing with the chain. I stand behind the bike (no way I am going to sit, what with doing this out on the road on a regular basis), wrap my left little fingers around the left chainstay, index and middle around the tire and just pull the tire back and hard against the left chainstay. Tighten the right hub nut with the wrench, handle down so it is pulling back. Straighten the wheel, tighten the left hub nut and check chain tension. I almost always have exactly the slack I want. (I never run the chain tight.)

Ben