some articles say to test the shoe for no shifting while sitting; walking in the shoe is pointless.
Any other advice on fitting a tri shoe?
How much movement should there be along the vamp? If I press my toes down hard should I be able to lift my foot slightly?
I was told that because manufacturers are constantly trying to make better shoes but also trying to keep the price down they often skimp on the insoles. I bought "off the shelf" custom insoles which you can heat up and then they mold to your feet when you put them in the shoes. I have found that once you have the right size shoes replace the cheap, flat, insoles with custom insoles and it instantly improves the fit of the shoe. If you can afford to get them done professionally even better.
you are right fit them while sitting, like you say walking is useless as you are not walking in them unless of course you are getting the tyep of shoes that can be used for walking.
the only thing i can say is that to simulate the shoe while pedaling, stand on the balls of your feet with the shoes sinched up and see how they feel overall over the foot. sort of like you would if you wore high heels, not that i wear high heels, but you get the general idea. LOL (maybe a female can put their input here)
also i have found that for pure tri shoes, most of them have very thin or nothing insoles. this usually for me doesn't pose too much of a problem as i don't need orthotics, if you do then its something you should discuss with your podiatrist, but i found that most tri shoes have thin insoles for the sole reason of draining more water quickly. thus the large numbers of holes in some of them.
compared to road cycling shoes tri shoes normally don't have as many straps so make sure that hte fit is what you want, as they will stretch a little over time. personally i prefer them to be snug to the foot over the entire foot except for the toes, in other words you know they are there but not constricting (still wiggle the toes around a little and not touching the front of the shoe) with very very thin socks on but in no way painful when fully sinched up. that way without socks they are perfect for racing.
other than that goodluck.