How to enter length information for ways?

I've been measuring trails in town simultaneously with a GPS logger and a distance-measuring wheel. As a result, I know the distances between trail junctions quite accurately. My repeatability seems to be around 1/4 percent. Due to the relatively high curvature of trails (both horizontal and vertical), inferring distance by doing the math on the way points is not as accurate. How do I store my accurate distances?

I see that there is a DISTANCE tag, but according to the documentation only applies to relations. First, you have to actually create a relation to use it, which I don't think is appropriate for many of our trails. Second, it seems to be intended to give the length of a longer route thru a bunch of intersections and possibly as it switches ways in the OSM database.

I was expecting to make individual ways between trail junctions, then use something like the DISTANCE tag to explicitly state how long that way is, regardless of what you might get by adding up the individual line segments that were entered by eyeball-filtering GPS traces.

Added in response to comments

I haven't directly compared my measurements to distances computed from OSM data, but I have seen significant discrepancies between the wheel-measured distances and distances computed from other people's GPS tracks, over 10% in some cases. That may have been because these other GPS tracks were rather sloppy, which is one reason I'm re-doing all the trails in town. It just seems a shame that there isn't a mechanism to save this data in OSM when known, but if that's not done then I will stop looking for it.

Trails are thin, so there is no issue of walking on the other side of a street. The biggest issue that will make the distance experienced by two people different is when they go around a wet area differently.

As for getting out of date when someone else edits the way, I can see the point to that. That is probably the best reason given to not add distances to ways.

I guess the overall answer is

1. Distances on ways is not how OSM is intended to work.
2. Even if you did it, it would cause maintenance problems as people edit the ways and then don't update the distances accordingly.
3. We think that the error isn't that great, and don't care if it is.

If someone wants to write a nice answer stating this and possibly elaborating on it, I'll be happy to upvote and accept it. I'm not going to upvote or accept SK53's answer since it didn't address the question. I asked how to store the more accurate directly-measured distance data instead of requiring it to be calculated, and his answer is basically "It's not needed since it can be calculated".