Look at he Kayak & Canoe Sailing Rig page. The sail rig 55 sq ft rig should fit a double kayak.

I've built a Sport Tandem with the latest sailrig and it is fantastic.

https://www.youtube.com/channel/UC3evMZcrGGGCWwonCBHOuHQ

and some other pics here at my website which is just starting:

www.smalltrimaran.co.uk

I moved the bulkheads in the floats and crossbeams further apart so you can get a full paddle strooke in but have now put trampolines across so we can keep it flatter and it flies along.

The larger rig is great, especially for a slightly bigger boat with 2 bods on it.

   Also look at the Waterlust Sailing Canoe, it has sails and a Mirage Drive.  Having owned three Mirage Kayaks, I am not a fan of adding a Mirage drive to an otherwise low drag boat.  The units themselves create a lot of drag.  For a low drag boat like an efficient tandem, you can go further and faster with much less effort by paddling.

   Please see my listing of the CLC tandem sail. After years of trying this is the best sailing setup for the tandem I came up with. It is fast and easy to reef(roll up) when in a blow. Call me 970 222 6812 if interested.

Regarding the Hobie Mirage drive, I had a Hobie Adventure Island which is where I got the idea of adapting its sailrig to my CLC tandem. It would be a crime to mess up the CLC low-drag tandem with that system. The added power of peddling vs paddling is great for the Adventure Island because it is like paddling a barge. Moreover, I found peddling that system was hard on my knees as it it not like a bike where you can reduce knee stress by spinning. Those flippers get caught on seaweed and I was always repairing them.