I recently moved my two 27-28" silver and a 20" black aro with the plastic bag method. The 20" black was a piece of cake and this method should work well for you. With the two silvers I had to double bag, the fish silver shot through the bag with just a flick of the tail. This happened before I could even start to close up the bag.
I moved my silver a couple years back when it was around 15-16" and used a pillow case. It ended up loosing a barbel and had a cloudy eye for a couple days. Would not recommend this method.