Pete,
After having torn up the mouth of a nice albeit too small to keep lake trout with a treble hook, I've sworn off the damn things are replace them on every piece of tackle I use. Also the single hooks seem to get hung up on the bottom and on lilly pads less often.
As far as hook size, the gap on the single hook should be approximately as wide as the gap across the treble. The trouble is hook gaps very from manufacturer to manufacturer and between hook styles so its best to compare. I'd say nominally a #6 hook, but compare.
For trout lures my favorites are little cleo spoons in 1/4oz and kastmaster in 1/4 oz. I've found the generally outfish spinners.
