similar story to gibsoni, I made an outrigger for a 16' canoe using 75mm pvc pipe. It was approx 3m long with a right angle at each end, pointing upwards, approx 200mm risers, then a right angle on the top of those that pointed back towards the canoe. 2000mm spacer was enough to join the outrigger to the canoe and still left room to paddle in between the canoe and the outrigger. I capped the ends of the spacer and made a completely waterproof flotation device. These were lashed to the canoe, 2 mins to remove/refit. If the kayak is balanced right, only the bottom of the outrigger will be in the water, not the front of the right angle, thus reducing drag. Before gluing it all together, I dry fitted it and tested it on a calm day just to get the measurements right.
You can lean into the outrigger, we had 2 guys on the side of the canoe and it hardly leaned over - but don't lean away from the outrigger - it hardly reduces the roll. We almost got very wet. The outrigger made it really comfortable, allowing us to stand and fish. That rig is down on Flinders Island now, I will have a look for a photo.