Re: Larger or smaller....
I think a small shooting guide (nearest the cork) is going to function as a bottleneck, because you are going to have some rippling and such as the line shoots through.
The most effective guide arrangement for shooting line I've seen was on a rod built up by Allen Crise of Glen Rose, TX. He uses a large shooting guide and then positions a slightly smaller guide somewhere in the range of 5-8" ahead of it. It looks a bit odd, but has a remarkable effect on smoothing out the wiggles in the line. I think it has to do with harmonics or some other part of physics I've forgotten about. I don't know that he's the originator of the idea, but that was the best line shooting 5wt I've ever cast.