I have an older logosol mill (http://www.logosolusa.com) and like it
alot. I use a Sthil 066 as power for my mill. As stated elsewhere do
use ripping chain. I use the Pico (narrow curf) chain re-ground to 10
degrees that logosaw sells. Ripping takes far more power to do than
cross cutting, a big saw is needed.

They also do make a jig that does what you want called the
"Timberjig", search their site and you will find it. They have some
video of it in use etc on line.

I milled quite a bit of old Black Walnut recently that a friend gave
me. The logs had been on the ground for years, looked like hell,
externally very baddly rotted, but it was only the sap wood effected.
The core of the logs yielded some great stock, so don't be discouraged
by it just being dry.

I have no economic interest in the Co, I just like my mill!