anyone rig a 5-point harness on a wooden highchair (like a Svan)?

[octmom]

I love our Svan highchair, but DD thinks it is hilarious to stand up on the seat as soon as she is done eating. She can wriggle right out of the three-point harness very quickly. Has anyone tried to rig a 5 point harness for a wooden highchair, like a Svan? I am looking for suggestions about how I might do this.

Jerilyn
DS, 10/03
DD, 3/06