Why don't you post the links as requested?
And say exactly which Shield pin you want to connect to which PORT pin. e.g. LCD_D6 to PA7
Life is considerably simpler if you use contiguous bits in PORTA. The library is already prepared for that.
Yes, you can use random pins. The macros become a bit horrible and slow. But hey-ho, if that is what you want. If you designed your own pcb, you would route the pins conveniently.
David.