I gave some thought to all the forces being generated and realized the most abrupt force is when downshifting at high rpm's. Ended up with 4 sliding engine mounts, in the pics you'll see the rear bottom was a challenge (channel in a channel) for disassembly & re-assembly clearances for the axle, brakes and adequate support. With the lower carriage I got a skid pan/protection to boot!. The failure of the swingarm was easy to see- not enough support across the swingarm from front to rear. Test drove it and couldn't be happier with the result. Still have the reverse lever to fabricate and putting 3 point belts in will require some additional tubing on the rollcage. After my wife gave it a spin she asked that I put somemore tubing/frame by the seat- she says she feels like she's going to fall out!! So maybe a swinging tube with a latch- like a door.
I posted a pic of the shifter cable mount just so you can see what's needed for chain adjustment and fine tuning.
rarerat- I managed to find some red paint