I painted my slann a couple of days ago myself and I see what you mean.
This is not a uncommon problem on metal models unfortunetly, so you have to improvise.
I used some green stuff and glue, making the slann sit in place and waited over night so the green stuf hardened.
It realy did the trick, though I think drilling a hole in the palaquin fitting the plastic rod might be the best sulution..