I got these cheap 5mm ones for my front wheels. Torqued them down properly the first time around, and one more after 300 miles or so. 500 miles and no complaints.
I'd also be interested in going 10mm in the back, though that means I'd probably have to get extended studs. The Ichiba 15mm V2 have extended studs built-in and as long as you have cut-outs at the back of the wheels you are all set.