After some discussion with some sidecar savvy folks.. I'm going to start designing a 100% removable subframe assembly. Going straight to the frame for the lower front mount is asking for trouble.
I'm going to start off with 1" square steel stock for material and go from there.
Here are the mounting points I'm thinking of using.
I'll duplicate the triangle stock with a triangle of my own and have a 1/4" steel spar running along side the frame tubing to the L shaped square tube frame I will have bolted to the lower engine mounts with steel ears.
I will run one square tube spar back to the center stand mount but I'm short on ideas on how to approach this one.
Run a bolt through the center stand pivot ( its hollow) to a u-shaped bracket that is part of the front assembly. Or keep it independent?
Here is how the exhaust affects the rest of the mounts.