So sorry to hear the bad news!
I dont think you can bind it top and bottom, it would evently get sucked into a sproket.
Wedge a piece of wood ( i know you have a chains saw!) between the frame rails on the bottom of the tub to hold the chain tight. You will have to secure it from moving back and forth, i would hate to see the carnage if it gets sucked under a sprocket, it my not come back out or wreck something.
good luck