I'm building a set of Trusses where the Kingpost is much larger than the bottom chord. I would like to cut the bottom chord in two and house 1in. it with 3in. tenons in a 10by Kingpost. I was wondering if this would still by structurally sound or not. The Truss spans 20' with a 6by12 bottom chord and a 10by10 Kingpost.
Thanks
Chris

If I understand what you're asking, then the answer is "no way". The bottom chord of a king post truss is in tension. A lot of tension. A 3" tennon has almost no tensile strength. This would be a disaster waiting to happen. CB.

I've seen pictures where this is done. I would like to know how to make it structural

big long hardwood splines through the kingpost or some kind of dovetail joinery?
would be better to break the kingpost somehow
i assume you are bringing the kingpost down for asthetic reasons(decoration?)

It is possible to break bottom chord (especially for steeper pitches), but you need to use either wooden splines or special metal connectors.

Either way your trusses MUST be analysed that way and your PE HAS TO focus on tension joints.

best regards
Michal Zajic
www.tfdesign.cz