TwoBonesIK and forearm twist bones (from CAT rig) problem

Hi guys!
I’m stuck with my character setup and his animation blueprint…
We need to control his arms using IK from hand position. It could be easy if only the arm were rigged just like a leg with 3 bones (upperArmBone, forearmBone, handBone)… But I’m using a CAT rig so the forearm is splitted into 2.
If I setup a TwoBonesIK node in the animation blueprint on the forearmBone2 (the one closer to the hand) and chose the targets weel, everything works.
But unfortunately I have a 4 bones chain… and two of them need to be considered just like if they were one.
I tried to use two IK chains: one from the handBone trying to avoid bending and one from the forearmBone2… but all go mad.
Do you have any idea I could solve my problem?