Just something to watch with the lower aluminum spar with the bend for the steering post. .
I've broken one a season and it's not ideal as you usually don't realize until your hood is removed which allows for alot of stress on the rest of the chassis. I'm by no means easy on my equipment but I also have my hood off once a week for inspection and maitenace.
My solution was to use a old steel spar and cut compound angles to clear the straight post. I've gotten half a season on this setup and it's running strong.
This is a photo of one broken spar broken the other cracked at the bend. Both appear to have fatigue cracked. If the wall thickness was increased I'm sure it would be fine.