Bearing in mind I'm driving on the other side of the road from you...
I've always found a car 7" H4 headlight to be fine on a bike. When I dip for oncoming traffic, I still have a kick-up of light to the left which illuminates the ditch and hedges, and in the countryside that's a good thing (those of you in deer-infested lands will know what I mean).
When cornering left, the kick-up is very useful, and when cornering right, I'm on the left side of the road, so the normal dip pattern illuminates far enough ahead around the bend anyway. I simply adjust the main cut-off to be as high as reasonably possible without causing any glare problems to other drivers. Even the flat-dip motorcycle headlamp cannot address that problem - it's always a compromise.
Personally, I think the motorcycle approved totally flat dip pattern is just a cop-out by the makers, so they can fit a worldwide headlight unit that's not sided for any particular market and it's cheaper for them. A flat-dip pattern isn't going to give any bend illumination on the left or right, so I don't see the point.
To get the best result, not just any old light unit will do, as there are some dreadful ones out there. I'm now using a Koito 7", which has a very usefully even spread of light without any distracting hot or dark spots.
These were fitted to Mitsubishi Shoguns and Pajeros in the late 80s / early 90s. There are plenty out there, for cheap, and you'd be hard pushed to find a better one for the money.
I've read good reports of the Autopal units, and as far as I know, they are copies of the Hella lamps of the 70s, which weren't bad. The Autopal factory seems to have done a good job of reproducing them.
I nearly bought Lucas or Wipac units, but was lucky enough to find a few Hella H4 units cheap. They're also pretty good. I'll be fitting them as my auxiliary lights, with LEDs in them to lessen the alternator load.
