Everything works now! This is what solves it in the function convertAndScaleLeapToUE:
float w2m = GWorld->GetWorldSettings()->AWorldSettings::WorldToMeters / 100.0f;
FVector vect = FVector(-leapVector.z * LEAP_TO_UE_SCALE * w2m, leapVector.x * LEAP_TO_UE_SCALE * w2m, leapVector.y * LEAP_TO_UE_SCALE * w2m);
this is something i tried at first but the thing i missed was that the size of the hand meshes has to be scaled with the same factor (w2m). So I just exported your hands to blender, scaled them and then reimported them and force replaced the old hands_lo and its skeleton with the new. I got a weird orientation error but it was solved by checking the box “TOas ref pose” under mesh settings when importing.