I eventually found the best clutch combo (which fts my driving style) to use CRF engine on 720:
Use the 3 weights provided by the Team Orion option clutch set for 720;
use Serpent option hard clutch spring (1.3 mm clutch tension setting);
use serpent stock clutch shoe (0.6mm gap setting).
I used Team Orion 2626 pipe. The pinion gears I used were 17/22 & spur 61/56.