I can post! I could not sign my friend off the site....
Yes the egg float. However, when the eggs are first laid they do in fact sink and lay on the bottom. It is after a little while that they become somewhat bouyant. The ones that float are actually a bit larger than you think. If the egg starts off as lets say 4mm they might increase in size to 6 or 8mm. This is when they start to "float". They do not float to the surface. They sort of become neutrally bouyant.
As for egg patterns...
most of your egg patterns have this quality built in already. They don't snk and drag on the bottom. The hydrology of the bottom currents keep the flies from doing this. Remember the yarns that these flies are tied with when put into the water to not sink either. I think that the hook is the necessary weight needed to recreate the "neutrally bouyant" effect of natural fish eggs.