I'm struggling with sizing dilemmas for Inov8s too. I like what I hear about them, but the idea of buying shoes without trying them on just seems absurd. I live 50 miles from the only Inov8 importer/dealer in Germany; he has quite a good selection, but his prices are about double what I could get them for on sale in the UK. So it's tricky.
I've bought other stuff from him, and he's a decent guy who runs a good business. Specialises in adventure racing kit, and is one of very few local sources of specialist lightweight gear. I suspect it's Inov8's fault, not his, that his Euro prices are absurdly high, so I have no intention of insulting him by going to his shop to try shoes on then buying them mail order elsewhere. But on the other foot, times are hard, and I don't want to pay double price for a pair of shoes if I can avoid it.
I did get to try on a couple of pairs on when I was in London a while back, and my impressions were:
- Flyroc 310s are the same shape as my feet and would be a good fit for me in my normal shoe size. I have moderately broad feet and like wiggle room for my toes. I would have bought them but the shop didn't have my size.
- Roclite 315 - narrow.
Small points can be killers. The Terroc 330 for example is said to have quite high cut ankles. I have very prominent (and strange in other ways too, according to a physiotherapist who once looked at them) ankle bones, and many shoes - for example my Salomons and to a lesser degree my Five ten approach shoes - can sometimes dig in there and be very uncomfortable. Otherwise from its feature list the 330 would have been quite high on my shortlist, and if I had bought a pair sight unseen I probably would have regretted it.
A while back I saw a very useful article by a New England adventure runner who has used lots of different Inov8 models, with comments on all of them regarding sizing, fit and suitability for different purposes. I'll try to dig it out.
UPDATE - here it is: http://team.inov-8.us/2008/06/inov-8s-ben-nephew-talks-shoe-review_8274.html
... no reference to the 390, but lots of good info about lots of other models