Could be a bad idea but thought it's worth a shot. Trying to make a pod using my drivers side heater vent

What filler would any of you recommend I use to try and get a nice smooth shape around the pod inside?

 

Have been googling about and come up with the idea of trimming the face of the vent first to get the shape and finish. Then pouring some casting resin into the back to fill in the voids and make it solid?

Anybody got any experience of something like this?

http://www.ebay.co.uk/itm/250g-Gener...#ht_500wt_1180