You can change between races on the day I'm sure.
Last 3 years have actually been fairly decent weather for July.
I had a 5year spell from 2002 to 2006 doing the half and at least 3 of those years were absolutely blistering heat, with the other 2 years just warm!
Did the 10k in 08, and 09, and I remember how the usual nerves before a race weren't there, as I was glad I wasn't doing the half
. Came back to the half last year, and despite my highest ever placing in a half (16th) I knew I should have been a couple of mins quicker, and was disturbed to lose 5 1/2mins from my pb!
The 10k takes the same route as the half for the first 5k, and then you have a gentle incline but very short couple of hundred metres, then a 3/4mile downhill bit to rampage down.
In 2009 they completely bungled the 10k finish. I was in a pack competing for 5th place with 2 others, and a key marshall wasn't in place. I went the right way, they went the wrong way. I went from thinking I'd benefit from this, to being gutted to see a few people who'd been behind me emerging ahead of me with about 200metres to go! I had to kill myself to beat one of them, and come a meagre 9th!
At least I'd done the full distance though...it'd be worthless if you were one of the people who didn't run the full course. Apparently only me and the actual winner in the top ten did the full course!
Could have been really bad if the winner hadn't had such a big lead. The results show about 30secs different, but in reality it should have bene 90+