Change of status from O-1 to Fiance visa??

[Katie_C]

Hi,
My fiance recently entered the country with an O-1 visa. I've heard that we need to wait at least three months after he enters the country before marrying, since he didn't enter with a fiance visa. But what about changing his status from an O-1 (which I believe works like an H-1 visa) to a K-1? Could we do that right away, or would that arouse suspicion?
Thanks.