In reply to plogan5:
My set up when using my shunt:
Rope doubled and tied off at the top i.e. have two strands.
One strand on the shunt, the other strand left free to abseil back down.
I use a grigri to connect to the abseil.
On the shunt, i have a prussik cord through the small hole to help release it.
Weigh down the rope (the one the shunt is going on) with rucksack/spare rope coils.
I tend to use a (semi) static rope. (The routes i have been trying, the crux is near to the ground, on a dynamic rope i would hit the ground on rope stretch).
Rope protectors if necassary.
Either remove the shunt for abseiling or just hold onto the prussik cord to release the shunt while abseiling back down.