Spark Plug Gap

Is it better to use the larger or smaller gap size when installing plugs or does it really matter?

As long as it is between 0.80mm and 0.90mm ( 0.031-0.035 in), I don't think it matters. Aren't you impressed I knew that? I'm impressed that I knew where to find my service manual.   

Go by shop manual

Always choose the smaller. As the electrodes wear away from spark erosion, the gap will widen with time.

Thank you Big Bird, I like your answer the best.
That was my belief and will be installing on the smaller side soon.

Bigbirds advice is good UNLESS you follow Honda's recommendation of changing plugs every 8K... In that interval the plugs won't have time to wear!!! Personally I think that 8K is ridiculous but that is what the book says. My Gold Wing has 32K on it and am pretty certain the plugs are original.

I replaced my SW plugs at 8K because I have the Honda 5 year warranty (didn't want any problems later). I set mine at .034 fwiw.

The Silverwing's ignition system uses only 1 coil to fire both plugs at the same time. That means both plugs fire together every revolution of the crankshaft. There will be a wasted spark in each cylinder on the exhaust stroke of each. Granted, the wasted spark accounts for almost no wear of the electrodes, as the flow of electrons does not have to battle the high cylinder pressure which is absent on the exhaust stroke. But the double sparking of each plug as well as the higher rpm operation vs the Goldwing engine could account for the 8k mile recommendation. I have seen plugs come out of the Swing engine at the 8k interval and they have been out of spec with too much clearance. I just Googled, and I see that the GL1800 uses 3 coils. That means it works the same as the Silverwing ignition system. So I will chalk up the extended life of the Gwing plugs to the engine's much lower rpm operation and lower cylinder pressures due to its lower compression ratio.