Re: Replacing 5/16 genoa sheets
Not in my opinion, no, weight isn't significant at that level.
Different folks have different values for significant. I don't think 1/10 of an ounce per will add signicant heel topside, or significant windage.
It's more about the 'hand' of the braid; and therein lies the significance. Some of the light weight uber strong new lines are so slippery you can't hand trim unless you have good gloves and grip.
So while sure, on your boat you could get double the price 1/4 uber braid and maybe gain .00001 knot of VMG you'd loose your trimmer and be out more money.
Assuming you are going for the basic 10 dollar trophy - is it worth it?
Lessons learned are opportunities earned.