Well, I'm 215-ish on a good day, but I dunno- you want to ride with me?
There's plenty of riders of all stripes in & around Portland. There's even
two recumbent clubs!
A couple years ago they added Clydesdale classes to the 'cross races:
http://bikeportland.org/2006/11/08/o...ss-cross-race/
Here's the results from a recent 'cross Clydesdale race:
http://app.obra.org/results/event/13311#race_146442
The BikePortland site and forums are good places to start getting informed about the local scene.
FWIW: this is not a Clydesdale, I think: