[Mac OSX Internet Sharing with WiFi Pineapple howto]

It would probably be easier to set the mk5's ip address to 172.16.42.X and let the mac have .1

[Mac OSX Internet Sharing with WiFi Pineapple howto]

once you've 'clicked' trough enableing ICS on the proper interfaces this will do the rest:

sudo launchctl unload -w /System/Library/LaunchDaemons/com.apple.InternetSharing.plist
#editing file /Library/Preferences/SystemConfiguration/com.apple.nat.plist
sudo defaults write /Library/Preferences/SystemConfiguration/com.apple.nat NAT -dict-add SharingNetworkNumberStart 172.16.42.0
sudo launchctl load -w /System/Library/LaunchDaemons/com.apple.InternetSharing.plist
sudo ifconfig bridge100 172.16.42.42 netmask 255.255.255.0 up”
cat /etc/bootpd.plist | sed "s/172.16.42.1/172.16.42.42/"|sed "s/172.16.42.2/172.16.42.43/" > /tmp/temp.bootpd.plist
sudo mv /tmp/temp.bootpd.plist /etc/bootpd.plist 
sudo kill -HUP `pgrep bootpd`

On Yosemite, you'll need to set SharingNetworkNumberEnd and SharingNetworkMask as well.

#editing file /Library/Preferences/SystemConfiguration/com.apple.nat.plist

defaults write /Library/Preferences/SystemConfiguration/com.apple.nat NAT -dict-add SharingNetworkNumberStart 172.16.42.0

defaults write /Library/Preferences/SystemConfiguration/com.apple.nat NAT -dict-add SharingNetworkNumberEnd 172.16.42.254

defaults write /Library/Preferences/SystemConfiguration/com.apple.nat NAT -dict-add SharingNetworkMask 255.255.255.0