Hi Jon, check out the ponies used in this video. I find saw horses too short for the reason you mentioned. I picked up this method from Steve Chappell at Fox Maple. Spread your work out. These are about 16 years old, and about 4.2 hands high, HH, well trained.
http://www.youtube.com/watch?v=QqxlO_0YqrY

Knots, take the time to lay out around the knots as much as possible, shift joinery up or down the timber, make a story stick with the pertinent joints marked out. It is worth having timber a couple feet longer for such reasons. The cut offs can be used as pony blocking, too.