A lot of people (myself included) backpack with a two-man tent. Its nice to have a bit of shoulder room and places to put things. I've come across multiple people that recommend a two-man tent. A one-man tent can get a bit claustrophobic.

Specs I found show the Marmot Twilight weighs 5 lbs 9 oz with all the bells and whistles so it is a bit heavier than some two-man tents out there but it is certainly doable. My tent weighs 4lbs (Kelty Ridge 2) and I'm overweight and out of shape. There is a good discussion (I think its in the Philosophy forum) that says the most important thing is to get out there and not worry about every gram. 20-30 years ago people would have loved to get a 5lb tent.