This is a technical question that is beyond my area of expertise. I think you want to direct this question to JR Shepherd in the GATE Glock Pistol forum
as this is more of an armorer question.
Having said that, I will give you my general impression on changing recoil springs. In my past I worked for Sig and spent a lot of time with the engineers talking about this very kind of issue. Besides the obvious "voiding the warranty" issue, you can also do long term damage to the pistol depending on the change in spring strength that occurs.
If this is a competition gun then there is more room to "tune" the gun to your particular desired goals. If it is a carry gun then I strongly recommend against making changes that are not well researched and tested.
The factory spring in the gun has gone through thousands of rounds of testing and been in the market place for some time. So it has been rigorously tested. Aftermarket springs often do not get the same level of testing, and certainly not customer-altered springs. Eyeballing the cut on the spring seems simple but it's impossible to know the exact ramifications of that alteration.
When you change a spring in the gun from factory to aftermarket you can lose spring life resulting in an increased slide speed after the spring has lost its strength. In the case of the Sig braided spring in the P229 – a platform similar in size and specifications to your G23 – that spring maintains significant performance characteristics after 5K rounds and has gone up to 20K without a failure. The factory spec allows for 1 failure (of any kind) per 1K rounds.
When an agency recommended using a popular aftermarket competition spring in their issued P229s, the Sig engineers did testing and collected the data that showed how the competitive spring strength almost immediately dropped off after 5K rounds. This would mean that the armorer for that agency would have to religiously change those springs at, or before, 5K rounds.
I know of one case at Sig where the springs in a gun were not replaced and the slide speed went from 5 meters a second to nearly 9 meters as the round count increased. This occurred around 30K+ rounds on the same recoil spring - which was supposed to be replaced at 5K rounds - and the result was eventual cracking of the slide due to excessive stress. Regardless of what path you go down, make sure you replace your springs at the recommended intervals, if not sooner.
Springs are not easy to manufacture and there is extensive testing that has to take place, even at the early design phase of a spring. Taking one of those springs, whether factory or aftermarket, and cutting it changes the dynamic of the spring considerably. While the pistol may shoot well and feel very comfortable to you after the alteration, the longer you run the altered spring the more you’ll experience unintended consequences of the change.
From a competition standpoint, it is easy to put faith in a gun alteration to gain an edge. The same is true in any sport where equipment come into play – think golf. But in the end, guys like Dave Sevigny, Max Michel, Bob Vogel and Matt Mink can take an out of the box gun with factory springs, factory trigger and factory sights and win. Their advantage comes from practice. Lots and lots of practice.
Hope this helps.