Exporting the FIT file from Garmin Connect and trying to upload them to 3rd party sites has been mostly hit and miss (more misses than hits). These 3rd party sites just _doesn't_ recognise the FIT file at all. (unable to process / no data etc).
(in my case, I'm just inputting power as a metric from my trainer power profile - using the nativenum of power so that it can be interpreted as power)
I've tried
Strava - Works (Power gets interpreted as power)
ridewithgps - unable to process
beginner triathle - uploaded successful but doesn't turn up.
velohero - No data
TrainingPeaks - Uploads OK. No Power.
I've also read from this forum that basically Garmin won't be "overriding" values that is native even tho Fit Contributor denotes that its's the same "like power". It will still be a developer field and will needs to be processed differently by GC or any other sites.
Then I've read (or heard) in a podcast that Strava and TrainingPeaks will not be looking at implementing looking at these developer data fields. Hence, looks like even tho the FIT file standard is owned by Garmin, other companies are not jumping onto the bandwagon for displaying 3rd Party or developer fields. (They joked that they won't want to display a metric that says "hookers per hour" akin to the "beers earned" metric)
Nett-Nett, somehow I feel that the FitContributor is going to end up a mediocre attempt at allowing developers to do things. (then again, if Garmin's objective is to ensure that ppl who buy Garmin devices _stay_ on the connect platform then yeah, it's great. I just wonder how many ppl actually only have GC and not Strava / TP etc and who will be syncing their data all over the place to multiple platforms.)
My beef with this is that while the developer fields are recognised in GC, it may not be (based on my limited experiment - seems like most sites don't or don't plan to) recignised in other sites. While this is OK that they don't do the "beers earned" graph, my pain is in that some of these sites don't even accept the FIT file likely cos either they havent updated their servers to accept the new FIT file format w/ the developer fields (whether or not they ignore it or otherwise).
That's the main beef I have now. some of these 3rd party sites don't even recognise the FIT file so I'm left with a data that is strictly confined to GC. (well, except for Stava and TP in which it uploads fine but my fav IOS app - cyclemeter doesn't recognise the FIT file)