I bought some Loctite. Will let you know the results. The bonded insert looks interesting as well, but I don't know if the fork is 100% identical.

I'm trying to think of the things that could be causing this. Did you use the SL7 bearings? Or the bearings that came with the bike? Also, did you sand down the paint on the fork so that the bottom bearing is sitting properly flush? I didn't use any carbon grease for the expander plug, but I did have to sand down the edges of it to sit flush within the stem, like This Is Dog suggested.

How are the gaps when you tighten everything up? Below is a picture of mine for reference.

I've used the SL7 bearings and the SL7 compression ring. I've sanded the edged of the cap so it sits flush. I think I did al the right things. It compresses fine at first, just slips a tiny bit after a couple of harsh gravel roads.

I can't imagine the stem slipping up. It's tightened to 6 Nm. It looks like the expander is coming up by about 0,5mm but it's enough to cause a bit of headset play. Hope to hear done other builders experiences with this frame and how they solved it.

This is completely clear and makes sense of course. However some users mentioned that the expander moves out of the steerer tube while compressing the system. I just wanted to note that the expander sits tight in the steerer tube in my case.

This happens to me as well. I'm able to put the stem on and fit the expander in the fork. But after tightening the expander and trying to compress the headset the expander comes back up out of the fork. This is making it impossible to tighten and eliminate play. I'm already using the SL7 compression ring. Any tips? Should I buy another expander (J&L perhaps) or use carbon paste. Any tips are welcome to prevent the expander from coming back up out of the fork.

I'm building one myself. Already ordered the SL7 compression ring. But good idea to buy quality bearings as well. What do you guys recommend?

I thought the hacksaw was the "crude" part, but sure you could use sanding paper. But it is very hard nylon, so you'll be at it for a while. The Dremel bit I used was also just sandpaper on a roll, but it went a lot quicker than manually grinding sand paper over the ring:

Hi, I just assembled everything, so I'll try and explain better. The Deda compression ring is higher than the original provided C-ring. So you need to shave a couple of mm's of the top of the ring. So you grind down the ring to the required height. The smaller bottom part of the Deda ring fits in the bearing perfectly, but if you leave the wider upper part at the original height you will be left with circa 4mm of space between the frame and the headset cover.

I tried to do my best to illustrate in paint . You need to grind the ring down to the red lines. So remove the purple material in smalls steps at a time to check if it is still high enough to compress the headset.

OK, so I fixed the situation pretty easily. I bought the Deda compression ring 45 degrees:



First I sawed the largest part of the top (circa 2mm I guess) with a hacksaw and then I ground the top down a smal bit at a time with a Dremel tool till it was at the correct height to compress correctly but also not leave a gap between the frame and the headset cover (there is still a very minimal gap say 0,5mm). I also used a Deda 70mm expander plug to get a bit more grip while tightening the top cap. No play anymore and a very cheap solution.