The pony rim is only 7 inches wide so the largest you want to go for overall performance is a nine inch(2 inches wider than rim general rule) wide tire which is 225 width. 225/50/16s look really good with a slightly smaller sidewall than stock.
Kevin
Speaking from personal opinion here: Anything wider than the 225 on a 7" rim reduces the cornering feeling a great deal. I have run both 245/50/16 and 225/55/16 and prefer the smaller tire