I just purchased a new Trek 520 that I will be picking up in a few weeks. I will be using this bike on a coast to coast trip next year on the Transamerica route. I am thinking about equipping the bike with a kickstand. After a little research these seem to be popular stands:
Greenfield single sided
Pletscher one or two legged kickstands
Clickstand

Any recommendations? I am leaning towards the a two legged stand like the Pletscher but not even sure this can be fitted to a Trek 520

You'll need adequate space between the BB shell and the chainstay bridge for a conventional center-mount and for the double-legged. I use both of those and the rear mount on different bikes. I've used a center-mount on tour with rear panniers and a handlebar bag. Last tour I began with the rear mount but with four panniers there was too much weight oddly distributed for the rear-mount so I switched to the double-legged center-mount. That still needed a bungee to help keep the front wheel centered when parked.



Random 'net 520 photo shows what looks like adequate space for the double but a current owner can probably chime in with confirmation.

I've got the Greenfield rear-mount stand and enjoy it.

You'd want to check to see if that could be mounted around your rear disc brake, if that's what your bike is equipped with.

I love my Clickstand for my 520.