Grammatical Conundrum

Was partly editing a proposal earlier on and encountered a grammatical conundrum. A choice between two:

1. Rationale for recommendation
2. Rationale of recommendation

To me, "for" seems correct and I have been using "for" in my other proposals, but reading another proposal today, it made me stop and consider whether "of" would be more correct.

After a hasty powwow with three of my colleagues who have been called "englishman" and "englishwoman" amongst us, and referencing to an ever handy super sized dictionary, "of" was more appropriate to be used. OMG!!! My "England" has been "cacat" in so many earlier proposals, and no one said anything!!! The funny thing was, when we were discussing, one of the answers given whether correct or not, was follow big boss's "england" (because he has to sign off the proposal). If big boss says "of", use "of". Don't have to think so much, so less headache!!!

Incidentally, just found out today that there is another common mistake I make when using the words "regards" vs "regard". With reference to something, it is always with "regard" to, and not with "regards" to. AH SO!!! Now I know.... I think I need to go back to english school.......