I'm also still trying to find the best way of using MRA/Tread/XT2. Tread will definitely not play nicely with gpx1.2 is the first thing - it's purely a MRA file that nails a route to your track in the Zumo. The shaping points are stripped so Tread will build its own route using whatever parameters are set within the app.
However, you can transfer gpx1.2 via cable but now I'm finding Tread will sometimes mess with those routes after a sync. I suppose a check before departure that your MRA route and Tread agree might stop this but what a faff. A quick workaround if you're on tour and it happens is to delete the route, re-import (as it should still be there if you haven't done another cable transfer), make sure it overlays your track then start the route immediately before another potentially route destroying sync.
gpx1.1: This is the file of choice and seems to work a lot of the time. Enough Shaping and/or Via points need to be used so that Tread builds exactly the same route as MRA otherwise your XT2 may refuse to calculate the route, though sometimes it will! I'm not over keen on Via points as if you don't go to them, the Zumo will try to route you back there. There is a 'skip' option but that can totally destroy the rest of your route. With both the above files, you will also be sent your track. As others have mentioned in previous posts, it's a really good idea to widen the track and put it in a visible collection where you can see any route deviations. Bright red for the track seems to show well in the XT2.
You can simply follow the Track or even create a route from it which will be accurate but you then lose any Via points you may have added. Fine a lot of the time.
I would like to be able to export my MRA routes in gpx1.1 via both cable when at home and Tread whilst away without Tread destroying all the good work. It would be great if you could only sync what and when you want. Disabling Tread means you lose everything else it provides. It's a Garmin problem, I know .By the way, if you haven't read elsewhere, you can now leave auto-recalculate switched on with gpx1.1 and it will bring you back to your route if you deviate. gpx1.2 will do similar but seems to prefer turning you around and sending you miles back to a previous point.
Apologies if this is all stuff you know but I'd love to hear any other suggestions anyone has to make MRA (or any other imported pre-built GPX route) and Tread play nicely all the time.
