I did something similar to what you are very wisely suggesting, in that I preceded the Lemon juice with 8 oz or so of plain water, then drank about half of the Lemon juice, then drank more plain water (several ounces), then mixed the last half of Lemon juice with water (About half anf half), then drank more plain water after that.
As soon as I knew I was going to keep it all down < g r i n >, I then brushed my teeth with baking soda.
Did another 5 Lemons tonight, which yielded about 400ml juice.
I plan to wait a few days before doing this again (Unless I change my mind :-)).