Hi
thorton
I've been looking in on your blog now and again. IMO, you should not get a heavy single-speed. I've ridden the Worksman over many years in the factory. They're tough all right, but they are not for fitness riding unless you can stay on rail-trails or other flat areas. I'm concerned you might injure your knees.
Find an older mtb and have road type tires put on it. Do not use fat knobbies. They are
much harder to roll when you are heavy. Again, it's the knees. I started back in July at 270lbs. I'm down to 225 now.
You'll have to experiment with a saddle and may wind up with a collection of failures. Here's my suggestion to you:
http://i3.tinypic.com/wvpusm.jpg
http://i2.tinypic.com/wvpv0h.jpg