use an exchange that charges less commission for a start and back higher odds at the bookies, although that doesnt guarantee you will lose at the bookies , just a higher probability
You could increase your turnover to win the cashrace at the moment. Aside from that it’s just about making a profit on the offer rather than with bookies or exchanges.
It’s not a desirable answer I know, but if you want to lose on the exchange more – take poorer value overall. It works the complete opposite way around if you are arbing…. all your bets will end up in the bookies as they are providing the value in their poorly priced odds.