Almost all truck stops have certified Cat Scales. I don't worry about saving a couple bucks on the second weigh in. I will fuel up when we are loaded and ready for the next days travel (truck only). Of course that weight ticket will cost me $10.00. Then at some point when I am getting fuel while hooked up, and the scales at the truck stop I am using are not busy, I will take the whole rig across and get my other weight ticket. I just keep my weight tickets in the truck and then in a couple of days when I have time I will pull them out and start going through the numbers to see where I am at.
I know doing your weights this way actually costs an additional $7.00. But to me it is worth it for the convenience of not having to drop my fiver in a truck stop parking lot in order to weigh my truck solo.