The HarborFreight food dehydrator (#66906 $30, currently sale at $25) will work with the central ducting partially blocked.
On Sat, 29 Aug 2015, Jay Jaeger wrote:
Ooooh. Thanks for the pointer to HarborFreight. I think I will pop over to the store with a tape and see if they have one out to see if it is suitable today or tomorrow.
ID is 12.5" So, it would hold up to about 8.75" square If you're going to use it regularly, consider adding a fan.