Found this on the Apple support forum.
"Internet Sharing is not configurable. At all. It always creates a network in the 10.0.2.0/24 block and routes it to 192.168.1.0/24."
So here's how I just got it to work...
Set your ethernet to the normal 172 address, and log into the pineapple.
Go to configuration, and change the pineapple's ip address to 192.168.2.254, and the gateway to 192.168.2.1, hit update and reboot the pineapple.
Now go back to the mac's ethernet settings and change it to 192.168.2.1, netmask to 255.255.255.0, and gateway to whatever ip address your wifi or whatever you are sharing to, mine is wifi, which is 192.168.1.133. Set a dns of your choice, I'm using google's 8.8.8.8.
Pings from the pineapple don't work, but I get the internets from my laptop connected to "bobsfreewifi"...
https://lh6.googleusercontent.com/-bMzue73P7sM/Ty1hRLDA3wI/AAAAAAAAC-o/lCJ__WVjtQc/s1152/jasagernetwork.jpg
https://lh6.googleusercontent.com/-den0m3a-4T8/Ty1hREF8X_I/AAAAAAAAC-w/YT7BRDWlw4Q/s1152/networksettings.jpg
https://lh4.googleusercontent.com/-Y6tkM9_JSsQ/Ty1hRBl2ByI/AAAAAAAAC-0/qadve5TxsiA/s1152/inetsharloin.jpg