Some thoughts from My side I potray them on a Picture... may be you like...

a CD RoadMaster will give you no big gain in performance as your engine is already pumping 16BHP and 200cc also does that just a reliable power band with long Touring capacity..
what you will not gain ?
Power ? no it will remain same as your modified engine
More Speed ? Ahhh no ... I doubt may be it would reduce becuase it has no cruising gear...
What you will gain ?
your 296 cc madiefied is making 16 hp and drinking feul at 11km/liter where as 200cc Does 30+km/ Liter (Very important Gain)
Better Power Band, CD Madiefied is zero power from 1k to 6kRPM and burst like Nuke Power above that which is fatal for rider where as 200RoadMaster power Band is equally distributed and a lovely experience to ride.
Better Long Life and Touring Capacity YES OFFCOURSE
Even Better Choice Would be a CD185 Engine it is High Compression and has more Horse Power ...
