Right then people for all you hill runners out there its the London marathon this sunday and I'm having a go!

What I'm hoping for is some advice as to what pace I should be running!

When I entered at the middle of Jan (club place) I'd set myself the target of getting under 3:15.
However recent half mara and 10 k times. 1:23.57 and 37:23 respectively indicate that I 'could' be looking at sub 3.
Now here's the but!

But due to niggling shin pain I haven't done much road training at all. In fact bar last week I can't remember the last time I ran on the road other than races so I'm lacking 18+ mile training runs I should have got in!

So do I head out at sub 7 min miles and try to hang on but risk a wall hitting hour for the last 10k?
Or got out at 7:20 ish and see if I can pick the pace (its a long way) toward the end assuming I'm feeling ok????