If your pans are sitting on a flat arch at the same level, you will be fine with a pipe connection. Half inch minimum. Solder some threaded fittings into your pans far enough from the ends so there is room for a union so you can take it apart. Also leave some room for a strip of insulator like fiberglass gasket between your pans so that flames don't squirt up in the gap and scorch your pans above the sap level.
John
2x8 Smokylake drop flue with AOF/ AUF
180 taps on sacks
75 on 3/16 tubing with shurflo
Eden Prairie, Minnesota