In actual riding terms, the effect of reducing the HA is that you are able to weight the front end with a little more confidence; on steep tight turns, the front is going to feel less like it wants to tuck under giving you the ability to get more weight over it, which gives you more bite and thus grip.
At speed, the bike will feel less twitchy although to be honest, you’d have to be going pretty bloody fast to really notice it.
One thing you may find though is that at speed, the bike requires less concentration to keep it going just where you want it. At speed, you tend to steer more by instinct rather than overt input on the bars, which means you are concentrating a lot more on keeping the bike doing what you want it to do.
I know that sounds a bit ‘fluffy’ but it’s the net effect of steering by weight distribution, body position and the alignment of your head, shoulders, elbows and hips. These are far less tangible that actually turning the bars thus I describe it as ‘intuitive’. You’re less aware of the actual inputs so it means you have to concentrate more on feeling what the bike is doing.
It can be mentally quite tiring; on one very long and very fast descent in alps recently I found myself getting mentally tired keeping up with the guide long before I got physically tired.
A slacker bike makes it easier to keep things in line at high speed as the bike is less sensitive to steering inputs hence it can be less tiring.
