Actually Daas Yochid, my father z”l told me that the pieces of matzah he handed out were substantially the same size as those handed out by his father. The point is that there was no emphasis on the amount of matzah to be eaten at the Seder. One ate an amount sufficient to show he was eating matzah at the Seder. The same goes for kiddush Shabbos morning on bronf’n. We drink a one ounce shot and not a full revi’is. One drink an appropriate serving of the beverage at hand. Same happens at Havdalah, which we also make on schnaps. That’s how it was done and that’s how I continue to do it.
BTW, my emphasis on preserving such folkways leads to one ironic “right wing” conclusion. Because I am in many ways culturally Orthodox, I’m opposed to any expansion of women’s roles in ritual. My opposition does not stem from any Halachik argument (for instance the Mishne Berurah says b’feirush that a woman can make motzi on bread for a man, but I’d never go for it). Rather it’s due to my desire to do things the way they were done in yesteryear. I’d want my ihr zeide to be comfortable in my home and he would not accept any Halachik argument that it’s mutar for my wife to make motzi. (MO ignores such folkway arguments at its peril, in my opinion.) I can adopt your code based insistence on shiurim. But then I’d also have no choice but to endorse a lot of feminism.