George,
If you reduced your ether to 25% and added 5% Olive oil I would say starting/ handling would stay the same but you would get less carbon buildup, then keeping 28% Total oil you could alter the ratio of motor oil to olive to get a clean running motor, the next step would be to try reduceing ether content and uping the kero , but from my readings and experiance little is to be gained with more than 60% kero in the fuel- most team race mixes max the kero about 55-60% and these guys are after both speed and fuel ecconomy.
My personal receipe is 10% castor,12% olive,20% ether and the remaining 58% kero.
Stewart