I'm with you there Party.
No staking plan can turn what would be a level stakes loss into a profit. Using a % of bank betting method as a bet basis when winning is all that is needed to steadily increase profit. A staking plan in that favourable situation will not provide a greater profit either. There is mathematical proof of that [from a mathematician] on this forum for anyone into maths.

I'm also with Don Scott. Offered $10 on a 4/1 chance I would not reduce the bet either [I personally would increase it with a rare 100% overlay like that] as by reducing the bet to $10 an opportunity has been missed. The only reason to reduce the bet is if the punter has no confidence in his own betting line. If that is the case all his bets are in trouble.