I know exactly where you mean and I agree it is kind of strange the limit is not higher since they widened the road. Was it the county or the GSP?
I ask because I have had luck before by calling the sherrif's office and politely asking them to give me a break and they did. I freely admitted to speeding but asked them to reconsider whether I had actually passed the sign changing 55 down to 45, because I kind of thought I might have been still in the 55 when he clocked me at 70. They were nice enough to change it for me, saving me some $$$.
I don't know if the situation is the same, but when they first opened the new 5 lane stretch of Houson Lake, it was 45 and they patrolled it like a hawk almost every day, still do. Then after about a year the signs changed to 55. Maybe just for the residents sake, to condition everyone they aren't going to tolerate higher speeds before they set the limit to the final number?
So bottom line is I think you might stand a chance of getting a break because I am pretty sure they are mostly in a "public education" mode for the benefit of the residents, who all lost half their yards due to the widening, as opposed to a real danger crackdown mode. Just trying to emphasize this new road is not a new speedway, although much improved. I drive that road at least once if not twice daily going to work and I see someone pulled over almost every day since it opened. So try giving them a call.