Jim:

Not knowing how bad the twisting is, it's hard to know what to recommend. You may be able to create a housing or open up the mortise to accommodate the offset tenons. There is very little stress on the sill joints, so if you can just make them go together (with a little slop) you might be OK. On the other hand if you can't join the sills so they lie in the same plane, you'll have to scribe all the posts so that you don't end up with a crooked structure.

Twisted beams can be accommodated in layout by the scribe rule method and to a lesser extent with square rule layout. For a good description of the two methods see the explanation at http://www.tfguild.org/ubb/Forum4/HTML/000003.html

[This message has been edited by Brian W (edited 05-05-99).]