I'll like to give a IMHO of Dutching. A betting system I have had numerous encounters with mostly poor results. Whether that had more to do with the fact that when I have turned to Dutching or betting on more than one horse a race, which seems to be the main effort of Dutching rather than exact and true Dutching [hard because very close to jump SP's are required and that is not always practical unless all a punter has to do all day is sit in front of a PC], my normal 1 bet per. race method has been having a bad trot and I'm getting desperate for a win without working out the [true] sums of the endeavor.

My experience backing more than one runner in as race is a zero sum game. Look at it this way; In a 12 horse race if you back one runner that you think has a good chance of winning [lets say 25%] at say $6. Do you double your chances of winning by taking another runner who also is at $6 [25% chance of winning] and considered the other main chance? Well of course you don't. Both runners can lose and your chance of a win by either runner is not 50% but poor maths. If one of them wins you have really taken $3 on a 25% chance as both horses still have a 75% chance of losing, independently of each other, except you have 2 chances of one of them winning which increases your chances from 1 in 12 to 2 in 12, a small improved difference in % chance of a win [not 50% or 6 chances in 12]. A big underlay. Do it with 3 or more runners and the problem compounds [zero sum game].

I would have 1 bet on the $6/25% chance and the same on another race with a $6/25% chance [this is an example for simplicity]. Why? Because a multiple bet loss of 2 bets rules out the possibility of 1 of those bets being used in another race on a $6/25% chance. I maximize my percentage chances of winning by single win bets at much better odds overall in the long run and avoid the zero sum game trap of flawed maths by multiple win betting in one race.

Even strict Dutching [price according to odds] has the a similar problem as the above example. The more horses you throw into the Dutch, the higher the SR required and lower the overall odds from the combined bets in one race.
Yes, you are improving your chances of a 'win', but only by dramatically reducing you combined odds without improving you % chances of a win to make up for the odds reduction, because the % chance of a win for each runner is not an additive maths equation. That's what sucks punters into the illusion, they wrongly think it is.

One thing always seems to be lacking from proponents of Dutching or multiple win betting and that is the maths reality. What on the surface seems to be a swing, is in fact a big slide and that's why you never see the real maths.