It is common for us to integrate timber frame trusses into our designs. Normally we have no problem obtaining an engineering stamp on the plans, since they are typically over engineered, however occasionally we will run into an engineer that is unfamiliar with timber framing and will require some off the wall change that he/she feels will "strengthen" the truss. Currently, we have a situation where the engineer is calling for 4, 3/4" bolts to replace the 4, 1" oak pegs we would use. My question is, is there any data available to help us come up with some "standardized" rules of thumb with regard to truss design? Tenon lengths, amount of relish, etc. are things we would like.

There is some info on just what your looking for in the Timber Frame Jionery & Design Workbook published by the Guild, some of it written by engineers. Hope that helps.
Mark Surnoskie