Yes, you should be able to hang on for the last 2 miles on race day, and I don't think you have to try to do the race distances or longer prior to then. I actually wouldn't suggest doing 11m each of the next three weekends.
I don't have time to get race distance pre-race thanks to all the shoe issues in August. I'm planning on doing the 11 miles again this weekend and next and then will take it down to 8 or so the week before.
I'm planning on cutting out my second Pump class of the week on race-week and just doing a 45 minute or so run that day instead at a nice slow pace so my legs don't stagnate.
The 11 miles haven't had any ill effects - I just find the final mile home (uphill) a little tough. Then again, by that stage, I've been running for about 1:45 with only half a litre of water to refuel. Some people have suggested taking some jelly babies or a sports drink after an hour or so mark. Thought I might give that a go today to see if it helps with the 11th mile fatigue