My seating height with a RYET saddle is 69,5cm (170cm tall and 79,5cm inseam height, Frame Size 52) and I'm right on the "Minimum Insert" line. So you are right, a 38cm seat post will be the better choice. However, I can't tell if it fits the seat tube, especially with a DI2 Battery.

I did ask mention the fork failure and was told:

'The front fork failure is an exception. The fork is broken so badly, it must be man-made, and definitely not a product quality problem.'

WTF? Pretty interesting how they try to wriggle out of a situation... The fork was already inspected by the guys where I will do the CT Scan of the frame. Their findings were more than clear on human-made mistake or production failure. They said this happens to forks of framesets in much higher price-ranges as well, so for me thats "ok". However, telling the story of me not being able to handle/ride that bike the right way sucks. I also offered them to take a look at the fork and investigate from their side, but it seems their not interested.

They can be happy to have a customer-oriented sales represantive as Vivian, but the guys behind the scene ... meh.

Already got feedback from TanTan (Vivian).

1. They will conduct an in-depth investigation into the fork issue of the TT-X68.
2. After doing so and finding the root cause of this material problem (if there is any) they will sent out a new and painted fork.
3. From the pictures provided they stated the frame looks ok and should be safe to ride, but checking every mm visually plus doing the "coin" test should be the next step from my side. In any case of noticable damage I should get back.

Lets see...

Hold a sec, looking again, there IS damage to the other fork leg higher up?
Can you say with any certainty that that was the result of the impact and not occurring at the same time as the other failure?
Not to cross examine you, but...have had experience with a few of these over the years.

The fork was fine on both sides when I started. When I approached the crossing it definitely felt like the left side snapped first under breaking. I took a "dive" and fell over the handlebar. I think the right arm cracked due to my weight going over the handlebar and having no support from the other side. I just had a look at the point where the hydraulic hose comes out of the fork and the material is not "bonded" but more separate layers. Anyway, I hope TanTan will find a good solution. The ride feel on this TT-X68 was very good.   

Oh jeez! You have me worried now. No prior crashes or major bumps against the fork?

Nope, no bump and no crash. I really took good care of it and I've ridden it just for a bit under 150 km...

It sheared at the caliper mounting location?

See below and resized I remember it first cracked on the left above the caliper. The thickness of the material in this section is really thin...

Hi there,

wanted to give a short update on the bike. Riding quality is great, as I said before it is a whole different story to a Votec VRC Pro. If it is anywhere near an S-Works I can't tell. However, I'm more than happy.

Couple of things I want to mention:

1. The rear bolt on the seat post was mounted incorrectly from factory and on the pictures of TanTan. Please mount it the way Specialized is telling you in there manual for the SL8. 3nm on the Front bolt and 6nm at the rear bolt.
2. Save your money and don't buy the computer mount from TanTan. The computer mount is cheap ABS plastic and the angle is not good. It's to steep! I got this one instead:https://www.aliexpress.us/item/3256808076328828.html?spm=a2g0o.order_list.order_list_main.41.3b825c5fNkqyhL&gatewayAdapt=glo2usa4itemAdapt

Silly question-when you built this, were you able to use the standard Shimano 160 adaptor or was there a unique one shipped with the frame? I ask b/c the actual sl8 has unique spacing on the fork that requires a unique adaptor. Just trying to determine whether its a difference or not.

There is an adapter included and it has the same looks as the one on the Tarmac. I couldn't use the standard Shimano one, but maybe I was just to silly

We await your first impressions on the road 

So far so good. I did not die due to this chinese frame nor was there any kind of technical failure (yet)
To be honest, I can only compare it to my Votec VRC Pro and the TanTan is sooooo much more agile, direct and fast. In direct comparison with the Votec you don't need any effort to get it going. However, this was just the first impression and the weather in Germany is not yet ideal for longer rides. But I'll keep you posted