I believe lean angle is calculated differently depending on what you are trying to measure.
- Lean angle for Harley until parts of the bike scrap.
- Lean angle in MotoGp is how far you can lean until you lose tire grip

 

Lean angle is measured when the first part touches down. Left and right are usually different

 

Assuming that this is at speed and not low speed maneuvers, I have 1" floorboard extensions on my Ultra and I never scrape unless I intentionally mean to do so.

Scraping floorboards is cool as long as you know what happens next... You start to scrape hard parts that don't fold or give way.

Proper riding position will cure your floor board scraping. Taking a riding class and learn to never scrape a floorboard again.
Look at https://ridelikeachampion.com/ and see if there is a ChampStreet class that is near you.

Or any advanced riding class.

 

Several years ago I was thinking of trading my Road King for a Heritage at a local dealership.
I took the Heritage for a test ride and on the way out of the parking lot I turned right from a stop sign and scraped the boards. I went another half mile to another right turn from a stop and scraped the board again.
Both of these were low speed right turns. As I rode I touched the boards down several times without trying because I was so used to the Road Kings steeper lean angle.
I guess my point is the Softails are low to begin with so when you change things like extending the boards it just makes them that much more prone to scrape.
BTW I kept the Road King due to the lean angle on the Softail.

 

The Road King has a 32 degree lean angle, the Heritage has 27.3 and 28.5 degrees, so yeah, a pretty substantial difference. I suspect it's all in the floorboards; my Fat Bob has the same shock and same ground clearance as a Heritage, but has 31/32-degree lean angles.

 

It’s also worth noting that the mono shock softails have more lean angle than the previous design.

 

I didn't check the earlier models, I was just quoting lean angles for the 2018+ monoshock models.

 

That sounds about right, no floor boards on the Fat Bob.