Warren, your one example with suspension appears to me to have less travel and a slacker angle with more rake than his!
Maybe for the street it would be fine, but who is going to drag their wing down pavement on purpose?
A typical launch zone is a pasture or beach. I sure hope the front wheel doesn't tuck on compressing and landing over rough terrain when all he is using is his knees to hold the forks straight. A steering damper for dirtbike triple trees could go a long way towards piece of mind here. Take a look at the dynamics at 1:58 when he compresses it.
It is a big step up from his first machine and you can tell some serious time was spent fabricating that thing. Can't wait to see it fly once he gets a prop rigged!
Any grease is better than no grease.
The best exercises are the ones you enjoy doing.
I strongly prefer vehicles without doors.