Making a haybale forkable

I have a forklift with a fork in front. I wish to be able to pierce a haybale to a unspecified depth, but when I lift it, I want it to move along with the fork.

The problem is that the fork is a child of the forklift group and doesn't have it's own rigibody, so I cannot simply parent the fork (I am willing to tag it or reference it, but parenting the fork wouldn't really give me my desired effect). I tried attaching a fixed joint to the fork, but the fork promptly decided it wants to bug out away from the main part.

The haybale needs to be pierced, but if lifted when pierced it needs to move along with the forklift, until it is laid on the ground again and made "de-piercable". Preferably I want to be able to lift it up again if i dont "de-pierce" it.

So my question is, how do I go about doing this? I am not expecting code samples, I know how to code, all I need are classes, methods and advice as to how to tackle this problem.

Any help is appreciated!