Rock The Bike:
Rejoin the chain.
Rock The Bike:
Cut a length of trashed innertube to the chain you cut.
Rock The Bike:
Drop the chain into the innertube all the way.
Rock The Bike:
Break the chain at the length of the loop you measured.
Rock The Bike:
Take a trashed chain and measure a loop. Remember to set the seatpost at the high end of the range where you like it.