I wore 3 pairs of Tech 6's in a row, all size 12. When I got Tech 8's recently I had to get a 13, which fit just like the size 12 Tech 6's do. I was glad I went and tried them instead of just ordering them, the size 12 Tech 8's were too small. I bet you will have to go up a size also, and I'd definitely recommend trying them if someone close has a pair in your sizes.
I've got to add though that I liked my Tech 6's at least as much as these 8's and will buy the 6's again next time.