Does anyone have a Hero card on hand: what are the traditional dimensions? Would a 4 x 6 toploader be too big to house them, would they be swimming inside? Would a 3 x 5 be better?

I use the 4x6 Ultrapro top-loaders. They are a little too wide (the hero cards are something like 3.5" x 4.5"), but the extra width allows for hero upgrades and equipment to be stored along with the hero sheet for easy record keeping.