I don't know if FSX is any different, but in my FS 2004 Cockpit 2D mode I leave the Zoom level as default; 1.0...
....in my Cockpit 3D mode I use 0.75 zoom level to get better visual access to most of the VC Panel...the problem is, it makes the outside view unrealistic!
F....G-BPLF.... 8-)...!
P.S. I am an unusual
Pillock Pilot, in that I prefer to use the 2D Panel view, to get access to ALL my instruments without scrolling around the Cockpit with the Mouse or Hat Switch, whilst I am desperately trying to concentrate on Flying..

..!
I also like the way that many of the Default Aircraft's 2D Panels can be resized, (reduced height), to obtain a better forward view!
Win 8.1 64-bit. DX11. Advent Tower. Intel i7-3770 3.9 GHz 8-core. 8 GB System RAM. AMD Radeon HD 7700 1GB RAM. DVD ROM. 2 Terra Byte SATA Hard Drive. Philips 17" LCD Monitor. Saitek Cyborg X Fly-5 Joystick. ...and a Briggs and Stratton Petrol Lawn Mower.