Windows 7: Looking for a smooth-scroll mouse

Hello,

I'm looking for a *wired* mouse with a smooth wheel scroll (as apposed to clicky/notched; not necessarily free-spin).
The Logitech M500 is slightly too large for me. The ideal length would be around 112 mm.

Soft and easily pressed buttons (left, middle and right) is also very important to me.
Microsoft has some smooth-scroll mice but I find the buttons too stiff.

***

The following lines are for semi-pros. :)

I have disassembled Logitech B110 and Logitech K120 and removed their springs.
The result is a great smooth scrolling (sometimes too loose though).

The Logitech B110 left/right "click-chips" are positioned slightly lower on the motherboard compared to Logitech K120.
So if I don't use a full palm grip, the Logitech B110 buttons are easier to press.
OTOH, Logitech K120 has a special spring for pressing the wheel and removing it makes the middle-click press very soft.
Logitech B110 uses a different mechanism and the middle-click press is really stiff.

Summery:
I'd like to have a combination of B110 and K120: left/right "click-chips" in a lower position on the motherboard and a (removble) spring for the middle-click press.

Do you know if the Logitech M90 or a similar model fits my wish-list? :)

I'd appreciate your help.

Best regards.