With Shure 215s and Westone UM2s and UM3Xs, I've always gotten the best seal and isolation with triple flange tips, but acceptable seal and better comfort with long Comply tips. I also have a set of custom silicone molds that fit on the same phones (with the center tubes from some used Comply tips to increase the diameter of the tubes) but they end up falling off the phones and on the ground too often, and the improvements in seal/comfort over either the triple flanges or the comply tips are marginal, so not worth the inconvenience. Although the triple flanges are my favorites for riding, (partly because you can clean them) I can see how they might be uncomfortable for some as they go pretty deep. In an effort to get more comfort for a longer period of use, I sent my UM2s to In Ear Customs for reshelling, but they haven't finished them yet. I'm somewhat skeptical, especially since the company is totally unresponsive (see the thread entitled "Cheapest Reshells..." for a recounting of the lovely customer service of this company) but if the result is good, it will be worth it given the relatively low price. I'm pretty sure that a custom is the way to go for comfort and seal, and if I had the wherewithal, I'd probably go with the ES5s, or maybe the JH13s. I might have gone with having my UM3Xs reshelled as they do sound way better than the UM2s, but didn't because:
1) They're still under warranty and I don't want to void it;
2) My skepticism re: the results; and
3) I couldn't face sending my favorite iems off into the apparent black hole known as "In Ear Custom" for an unknown period of time.
I'll post the results when (if?) I get them back. As to the wisdom of iems on a motorcycle, In 30 years, I've never had a helmet that attenuated any appreciable amount of the wind noise from riding, and have the hearing loss to prove it. Said wind noise pretty much blocks out most other sounds anyway. I have however noticed that I've been surprised by emergency vehicles because I heard them late, but the same thing happens in a car with the stereo on so.... (shrug).