While the recovery kayak described in the 10/98 Sea Kayaker is a great design for its purpose, I would think that the 25" beam is too wide for a child. In addition to awkward paddling with hands hitting the deck, the boat would probably be unstable in a cross-sea - the child would have a hard time leaning the kayak into the oncoming wave which could push the boat over.

My 9 year-old son (about 60-65 lbs) paddles a 13.5 foot, 19.5" beam boat that is just right for his hips and shoulders. Should last him up to about 100lbs or another 2-3 years.

I imagine you could scale a Guillemot down proportionately to around 14 feet and have a fine boat.