Yes, this should work. However don't forget to flash Google apps for ICS (link in the post you linked) if you want to have access to Google Apps and Google Play (formerly Market). You also don't need to flash kernel in the case you described.
I would suggest the folowing scenario for you (based on nogoodusername's scenario from the post you linked):
1:Head Over To Stable recovery
3a:Install ZIp from SD Card
3b:Select ICS(Defy) .zip
4:Clear Cache and Dalvik Cache
5a:Install Zip from SD Card
Last edited by stanwise; 8th March 2012 at 02:09 AM.