How best to take advantage of these selections?

At the moment i am dutching for a profit, this means equal profit no matter who wins, sounds simple enough, but what if we have a situation like Black Caviars race where the prices have a huge difference or take today's race Wangaratta race 6 the 2 horses were priced at $3.90 and $17.50 dutching these would return me about $20 profit splitting the stake would return me $9.50 and $77.50 profit.

Big difference on the longer priced runner, is there more options i was thinking maybe bet in units depending on price, your thoughts.