OTOH, I agree with Kodama. For a non-custom fit, close counts. The first basic is the stand-over height. EVERYTHING else on the frame can be changed. (There ARE other frame issues if you are on the edges of the bell curve in the area of body proportions and/or size, where this may not work so well.)

Thirty plus years ago, when I bought my first 10-speed (I didn't know much), a Peugeot UO-8, I did the stand-over test and bought the bike. I was, perhaps, lucky in that there was no need to change the stem length. It was good as was, it turned out. I adjusted the saddle height and have ridden it over 100,000 miles.

When we recently (a couple years ago) bought three Trek 520s, again, we used the frame size as a guide. What we were really buying to fit was the frame. I made no changes to my bike after getting it shipped home (we bought in Seattle on a visiting trip and live in Juneau AK). We replaced my wife's stem, after some riding, here, with a stem 2 cm shorter and with a slightly higher rise.

One of the three bikes was for our daughter (as a gift), who was not even there to stand over the bike. But, I knew my frame size was good for her, but that she'd need a shorter stem. So we had the bike shop swap. I guess right on the stem length, so some knowledge helps.

We needed bikes for a tour in Europe. I wanted three identical bikes so I only needed to bring one set of tools and spare parts. She had outgrown the bike she had. And, I didn't feel out old Peugeots were suitable for loaded touring. We really appreciate the index shifting and 9-speed cassette.

Maybe we were lucky, but we are all still enjoying and are very comfortable on the 520s purchased without a test ride. So, it is possible. (This is not to discount the value of test riding. Just offering my experiences.)

Now, would I BUY a bike mail order or via the web? I don't think I would. I really want to see and handle the bike. See for myself what parts are hung on it. It was side by side comparison that allowed me to feel confident about chosing the 520 versus the alternative in the bike shop. If my 520 got mangled, some how, I might well buy another, sight unseen, because I'd be pretty confident about what I'd be getting.