Marc you ignore all sorts of variables.
Longer Wheelbase always makes it harder for the front end to come up. But seat position and motor strength and position of the belt in the front and rear pulleys and clutch engagement are all much more responsible for uncontrolled wheelies. My front end comes up on my 4 inch stretched hobbit at takeoff if I let it. Every front end should come up if youre giving a sudden burst of power that overcomes the front end weight and seat position leverage.
If my built 70cc hobbit had the stock length it would be barely rideable without adding weight to the front end or leaning over the bars at every takeoff. My built 50cc would lift its front wheel fast on the stock stance to the point that I had to change the tune in order to ride it.
Your obsession on stock length being somehow better or more stable is mega wrong on its face but whatever. I’m the unhinged one here I guess.
If Alex’s seat was right over the rear wheel the front end would come up bad even stretched. Why? Cuz the front is light due to the riders weight being over the back wheel where it should never be unless you are stunting. I really don’t think you understand physics.
I have one incredibly fast light short bike. Its really scary. But the front wheel doesn’t lift. Why? Because I moved the seat way up so all the weight is planted in the center and there’s no way the engine can overcome it to throw my fat tits off the bike. It’s extremely stable, but not because of the length. Its because of the weight distribution. If I stretched it it would still be just as stable or more with the seat further up. (edited)