Requirement of Bread at Shalosh Seudos

At first glance it would seem one is required to eat bread at shalosh seudos just like at the two other meals. So what do those who do not eat bread rely on? Furthermore is there a requirement for Lechem Mishnah (two whole loaves like we require on friday night and shabbas day)? Obviously it is always wise to be machmir and try to eat a Kzayis of bread and use Lechem Mishnah but for those that wish/need to be lenient what can they rely on? For those that enjoy math and riddles this is for you: We all know that on friday in the desert every Jew got a double portion of mon (man, manna..there's no real to spell it in english i guess). Chazal say that eat piece of mon was converted into two loafs of bread. So if you got double mon on friday that left you 4 loaves. You most probably ate one friday morning, used two and ate one friday night, used the remaining two and ate one shabbas day- so come shalos seudas time you only had one loaf left. This is the basis for the Tur and Mordechai allowing one to use just one loaf. Next week we will try to find out if one can be even more lenient and eat only Mezonos or maybe even Shehakol. Have a great shabbas. Q of the Week: What other shabbas halacha do we learn from the mon? Answer to last week: What Shabbos this year would it be assur to eat bread? This year Erev Pesach is on Shabbos and by the time shalosh seudos comes around chometz is already assur to eat.