The Logitech G5 for example, it has these two 'thumb buttons'. Well, they were nicely put OUT OF THE WAY for those of us who hate them, but where they are for those who want to use them is just stupid. You have to remove your thumb from the control grove, and shift it way up, arch it over, and then press one of two very stiff buttons. Who was the idiot those thought this up?
The G5 also has these two nice little buttons at the base of the wheel. THOSE are easily pressed! And would be great if they were NOT hard coded to ONLY adjust the speed ratio of the mouse So, they are great accessible buttons, but cannot be used for anything useful.
I think you need to understand that not everyone holds a mouse the same way you do. For instance, on my Logitech MX1000 Te thumb buttons are great. All three are easily reachable, aren't easy to hit by accident, and don't require me to lose my grip or any control on the mouse. The buttons above and below the wheel are impossible for me to hit though without almost entirely taking my hand off the mouse. So I DON'T want buttons for my index and middle finger other than the standard first and second button.
Anyway, I'm sure your method works well for you. I just wanted to remind you that people have different choices and preferences.