I suggest you check out <a href="http://forum.pesinsight.com/showthread.php?t=10944">this thread</a>! There are loads of cool findings and it is a thread that made a breakthrough for my ML team, finally entering 5 stars and able to win a lot! I went from a 4 back line (chealsea, but no original players left - part from Cech, and glenn johnson) to a 3 back line and pushed my right sb (dagaka!) up to play smf and cmf with A+B formations respectively. This also made it possible for me to push Martins in from the side (he's a winger) adding an extra cf to play the edge of the box. I did a few other adjustments (pushing up left smf - Cardason/Farzel Gart) to play more center as omf, and moving my default omf (Cesc) further to the right.. weew!
Being able to switch formations is a fantastic feature with PRO EVO - it has meant for me to go from narrow 1-0 wins or draws (plus the odd loss) on 4 star, to battle out solid games of 6 goals (but not all mine, mind!) on 5*.
Anyways, check out the thread about advanced formations and you will see the light like I did.
cheers -