i would wrap it now
but i'm not a fan of using foil. i think it sogs out the brisket and ruins the bark
most folks use uncoated butcher's paper. you can also use parchment paper
but... both of my granddads used brown paper grocery bags. they "breath" the best
don't worry about coming to 203° some briskets take longer to get to "poke" tender
might be as high as 210°+
"poke" tender is the true test. it should feel like a stick of butter left out on the counter
some folks have a stainless "poke" rod - what most of the famous central Texas bbq places use
Aaron Franklin just uses the point of his Thermapen digital thermometer (watch his videos)
i have a fancy pointed chopstix that i've used for many years - same shape and point as the stainless pokers
here's a pic of my plastic chopstix. i sharpened the point in a pencil sharpener
and my Thermapen digital thermometer
the first RULE of Brisket is - it ain't done til it's DONE 