I think the 5 x 2 work out at that pace is something you'll be able to handle. Your tempo pace is probably in the low 5:20s, so that gives you plenty of cushion. One alternative is to break up the 5 x 2 into a 3 x 2 segment and a 2 x 2 segment and do the first segment after just a couple of miles and do the last segment towards the very end of the overall run. That will get you the same overall volume, but would make the work out a bit more manageable. I also like the mental benefit of having to go hard late in the work out. I do a similar work out where I do 4 x 1 mile upfront and then 3-4 x 1 mile on the backend; but I do those at tempo pace rather than marathon pace. But I do think that you're capable of the 5 x 2 right up front in one big block based on your past workouts in recent races. Sensually a marathon pace because of the little breaks.