My 'halves braking distance rule' number was based on my own riding position on the drops. If you ride a bike with a different geometry, say with risers, then your centre of gravity will be higher and it will reduce the effectiveness of the rear brake further.
There is also a discussion on the link about how you initiate a skid in the first place and how it changes braking distance. People tend to shift their weight forwards to make it easier to initiate the skid. The further forwards you lean the further you'll skid.
So, depending on how you skid, it can only be worse than the 2x number. I was trying to show best rear wheel braking vs best front wheel braking.
My 'halves braking distance rule' number was based on my own riding position on the drops. If you ride a bike with a different geometry, say with risers, then your centre of gravity will be higher and it will reduce the effectiveness of the rear brake further.
There is also a discussion on the link about how you initiate a skid in the first place and how it changes braking distance. People tend to shift their weight forwards to make it easier to initiate the skid. The further forwards you lean the further you'll skid.
So, depending on how you skid, it can only be worse than the 2x number. I was trying to show best rear wheel braking vs best front wheel braking.