Hi Hackster.
I have the Garmin 520 and I have a Garmin Instinc Crossover Solar. I can not get the 520 and the watch to connect to one another for the hartrate function. In other words whentever I ride I have to use both to record the ride and at the end of a ride I need to delete one of the activities from Strave. Not sure if I am doing something wrong, but I need to buy a HR monitor for my Garmin 520