@Caty
I'm guessing that the grey line is 3590 and the green is 3490 with kunix's flash then. Interesting as a side-observation is that the 3790 [red] seems to be more consistent than the 3590 [grey] if that's that case.
@all
It would be worthwhile to test 3790 against 3490 in adverse 'city canyon' conditions so i'll do a side-by with those 2 in the big smoke when i can. The area used yesterday has quite big trees in places but there's nothing quite like the satellite signal blocking effect of tall buildings, is there? I really don't want to venture into the city with 4 devices strapped to the windscreen though. I attracted some unwanted hard looks from Sunday afternoon power walkers and joggers while driving aimlessly around in their leafy suburb and i'm sure more than one of them noted down my plate number 'just in case' after i had passed them several times. I didn't quite look like this, but it felt like it:

d2e13232cb344cd7f61ba15df8c9c53cd03ca46bc72df159211d2989048b5d034g

Maybe i'll reconvert the 3490_kunix later to conventional fw 3490 and add it in as well.

@Giomen
Huh???? Green line in Caty's google maps, i'm sure, is the 37>34 flashed with kunix's modded fw [34x0 with 37x0 gps fw].