Am I right it saying the Redstart is the donut shaped one with a bracket that attaches to the back. If so then I had one in the shed, they don't plane and theres little point putting anything bigger than a 2HP on it, you open it up and the outboard dissappears over the back
Having said that, they are fine as a yacht tender and cool for exploring rivers and harbours. I would recommend something a bit bigger with a transom and inflatable keel / air deck, combined with a 10-15hp this will provide alot of fun. A number of members including Phil Davies, Codprawn, and MeMe all have boats along these lines, may be worth a PM to see how they find them.