When you get flames at switchover, it's usually because pump pw is too high.
If a lower pump pw doesn't seem to work for you, instead of raising it, you should raise preheat fuel %
Raising pump pw increases the fuel sent to the igniter, which won't be able to burn it all, and the unburnt fuel will pool up in the engine waiting for the rpms to spool up (that happens during switchover) and then it will be sprayed outside the engine and ignited. Raising preheat fuel, instead, will send more fuel to the vaporizers, which will be able to burn almost all of the fuel properly, avoiding pooling.
So to sum it up, lower the pump pw and raise preheat fuel.