After more discussions with mtnbikebend on mtbr.
http://forums.mtbr.com/27-5-650b/chinese-carbon-frames-650b-edition-820784-15.html#post11082757

It looks it is relatively easy to pass the cables for the rear derailleur.
The bottom hatch below the BB looks to be there to help on this.
You can re-route the cable through the frame without using the housing that came with.

And crossing the cable in front of the bar, to get a nicer bend is ok too.

In addition he used the ESI grips, and cut them to the right length to cope with the Gripshift and have the brakes at the right place.

All this is obviously still theory for me, but in a couple of weeks, I'll try!

jonxmack, Not sure if that may help you, but someone posted this on mtbr:
http://forums.mtbr.com/27-5-650b/chinese-carbon-frames-650b-edition-820784-15.html#post11082757

The 196 looks to be the 650b equivalent of the 256 frame.
I PM'ed him yesterday, and 3+ months later, he really loves is bike with the rigid fork.

From what I understood, I don't think putting a shorter fork is about dropping the BB a few millimetres.
But you are nearer to a wheel of a shopping cart. Making the bike more unstable.
While putting a too long fork, the bike will be harder to turn.

Yeah I was surprised by the weight related answer too.
UD is a quite boring finish indeed.

For me 3k is the one that look the most "carbon" of all.
But only UD was available for the X-256 frame.

As a consolation the other carbon parts will be 3k.
And the Lefty tube is 12k.

Here is an old post on weight weenies about alternate grips for a gripshift.
http://weightweenies.starbike.com/forum/viewtopic.php?f=1&t=111890

It looks we can cut the grips to the size we want after all.

Just a doubt, when checking again the picture.
Is it just while waiting, or do you invert the brake levers right-to-front, and left-to-rear?

Another question to everyone, does the internal routing can be hacked, to allow to cross the hose/cables in front of the bar?
Entering the rear derailleur cable from the left of the frame.
And the rear brake entering from the right of the frame.

I will start my build with a gripshift too in a couple of weeks.
Could you post a picture on how this looks assembled?
It will alleviate my impatience

Peter, the light-bicycle.com web site is public, they do not hide anything.
http://www.light-bicycle.com/the-more-detail-about-hubs-MTB-hub-and-road-hub.html

I related what happened, as it may help some people know there is a lefty compatible wheel builder.
Don't worry, you are by far the darling of this forum. It just didn't work between us.

The Honsen website is also terribly slow.  Looks like just another me too trading company that also posts false information if they say they are using T1000 carbon when, according to Peter, is unlikely since no Chinese manufacturers have access to T1000 carbon.

May be we can give Honsen the benefit of the doubt.
Until we see what kind of frame I get.
So far, everything looks to go well.
Ok, the moment of truth will come after my first big jump, ending on a sharp corner.

T1000 and T800 is just the stiffness of the carbon fiber.
The fiber/resin fraction, and how the sheets are layered in the various parts of the frames are more important.

My choice may look odd today. But end of May, I was turned off by Peter when he told me there was nobody building wheels with Lefty's hubs in... China.
This didn't give me a trusty image as I just saw a couple of hours later that light-bicycle was building them.

Then from the posts on mtbr at that time, the leading time for the IP-256 was quite worrying.
They did not even reply to the people who ordered them anymore.
So I tried Honsen as Leo was responsive and very competent too.