quick spring question

I want to attach a head to a body via a spring so the head will bob around as the body moves. I thought I had this working before but now that I have re-sized the head and body I can't get the spring to stay straight. As soon as the body tips a bit the head rolls to one side or the other bending the spring with it. The spring is set to stiff and I've tried different strengths but if I set the strength high enough so that it wont tip over, I get no spring out of it.. Any ideas?

I've tried a bunch of different things but still having the same problem. Its like the spring stops being stiff and flops over when the figure starts moving. I'll post a picture in a while to show what I mean. All I want is for the head and body to remain parallel regardless of the angle the body is at but allow the head to bob up and down.. Maybe the bolts moving the arms and legs are somehow pushing the spring out of whack? Can't figure it out maybe ill have to use some movers and rotators instead but a spring seemed so simple and it was working before somehow..

Can't you just put a gyroscope on the head to keep it upright?

Try attaching multiple stiff springs. You can make them invisible in play mode.

Thanks for the advice but nothing seemed to work. I built a test figure so I could clearly see what was going on and here is what I found. If you attach two objects with a stiff spring the spring will do its best to maintain the same angle. I made a 1 layer deep square object that rotates back and forth with a circle object attached by a spring. Then I made a larger hologram thin layer square in front and glued it to the stone square, then attached 4 stone "limbs" via wobble bolts through the hologram material. The limbs tipped and turned the stone square and the stone circle followed perfectly with the spring maintaining its angle the whole time. Then I moved the limbs closer to the square and re-bolted so that their corners of the limbs would slightly intersect the square on full rotation. Sure enough the spring angle changes even though the joints of the spring remain parallel. Must be that the spring doesn't register that extra movement on the piece it is attached to? Anyway I found it interesting and glad that problems over. All I had to do was space the limbs further from the body so there was no contact. Also while I was just in create mode and paused I swear the background noise changed to kind of radio static and faint police siren for about 10 seconds then switched back? Anyone ever experienced that? It was really weird maybe I've been in create mode too long lol..