So I installed this little tool here yesterday: http://www.performance-pcs.com/der8auer-intel-9th-gen-oc-frame.html
 
But I cannot get my CPU to run with it, I'm always ending up in a bootloop with numerous Q-Codes showing. I've unmounted/remounted/readjusted the tool multiple times and went between stock frame and OC frame back and forth. My CPU runs with the stock frame, but not with the OC frame.
 
My waterblock is the Heatkiller IV, I've tried very light pressure (tightening the screws), light pressure, and no screws at all, makes on difference. I'm using LM between DIE and block.

what do you mean?

I have smilar setup. Heatkiller 4 and delid die guard from aliexpress. Make these work without problem. What I do?
1. Delid the cpu
2. Put 2 layers of electric tape around die carefully exposing only the die
3. Put the die guard on the cpu
4. Turn it over and pressing from top, sanded (lapped) both die and die guard together until cpu die height becomes around 0.4 mm
5. Of course because die guard is made of aluminium, later I coated the guard with black spray paint for LM not to get a reaction if touches bare aluminium 
6. Trim corners of the cpu socket. To make this safe I cut hard paper exactly the same size as socket and taped it on the socket gently for no pieces go inside socket. Because you don t want spray air inside socket, pins can bend
7. Sand the bottom of the Heatkiller 4 until all surface flat touching the die guard (not only the part touches die, because you want even pressure on the cpu corners), copper gets exposed, I don t care about LM copper reaction. And yes it is convex. So not possible give even pressure on the cpu.
8. Clean the 2 layer electric tape on the cpu pcb, and apply 1 coat electric tape this time. I used Global brand 0.13 mm tape. So theoritically when pushed down, die needs stay 0.13 mm higher than the guard, and make sure touch the plate good
9. Secure the cpu in socket with die guard. And you need different screw head because the big hex screw touches heatkiller plate.
10. Because the die guard is thinner now it bends around the die a little when you screw it down, but no problem because heatkiller' s perfectly flat plate will push it down. 
11. I cut clear scotch tape 3 m exactly the same size as die, and put it sticky part looking up (to stick to heatkiller plate), 
12. Put the heatkiller on the cpu (I also bought heatkiller backplate, perfectly secures the cpu block) no needed any mod on screws. 
13. Press down with hand and take out to see the tape on the plate.
14. With razor gently scratch around the tape, and take off the tape, now you can see where exactly your die touches the plate of the heatkiller
15. Clean the top of the die and the bottom of the plate with alcohol or acetone last time,
16. Apply LM on both surface
17. Secure the block on the socket. Thigten the screws of the block until you can not turn anymore. Stays around 1-2 mm upper than the limit of the screws.
18. Attach the cables of the mobo, connect it on monitor and press power to check if everything good before putting the mobo in the case.
 
Hope this helps you or anyone thinking about direct die cooling.
Later I can post some pictures about how cpu stays inside socket with die guard. Because I m new member I can not post now.
 

That is probably correct if you are not planning to lap the die. These frames are made thick enough to press down the pcb into the socket witout getting deformed. Without any die lapping height of the die and the frame are good enough to clear the socket corners. 9900k pcb and die is higher than older cpus. But if you decrease the height of the die, you need to trim the corners of the socket and also lap the frame. Because socket corners touch the water block first when you press down the block before you get enough mounting pressure for the cpu. And I m sure this derBaurer frame is also made for 0.8 mm die height. Not for 0.4 mm. Lapping the die inside the frame also gives you a chance for using the frame as a guide. And they become perfectly flat. And of course you need to lap the water block also for even contact with the frame and the die. So in my experience, for every cpu die lapping attempt, you should use a new die frame for guidance. And lap together.

I agree with you, just wanted to say: if someone wants to lap the die like derBaurer did, makes the die height around 0.4 mm or less and use the cpu naked, then may need to trim the corners of the socket. And also lap the frame to be the same level as the cpu die. These frames are for standart soldered dies. Not for lapped ones. I believe if someone can take the risk of lapping the die of an expensive cpu, and use it naked with LM, then probably will trim the board socket also.

I tested again and it works without ram OC, as soon as I apply any kind of ram OC i'm getting boot loop.